User:Marshallsumter/Radiation astronomy1/Microwaves

Astronomy specifically focused at the microwave portion of the electromagnetic spectrum is microwave astronomy.

Microwaves
Microwaves have many applications in astronomy and here on Earth. They are used for radar images like Doppler radar and weather forecasts. They can also be used for cooking and heating up food in your own home.

Optics involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.

Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz. This broad definition includes both [ultra high frequency] UHF and [extremely high frequency] EHF (millimeter waves), and various sources use different boundaries. In all cases, microwave includes the entire [super high frequency] SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum, with [radio frequency] RF engineering often putting the lower boundary at 1 GHz (30 cm), and the upper around 100 GHz (3 mm).

Planetary sciences
These three radar images of near-Earth asteroid 2003 SD220 were obtained on Dec. 15-17, by coordinating observations with NASA's 230-foot (70-meter) antenna at the Goldstone Deep Space Communications Complex in California and the National Science Foundation's (NSF) 330-foot (100-meter) Green Bank Telescope in West Virginia.

The radar image on the left was obtained on Dec. 15 when asteroid 2003 SD220 was 2.8 million miles (4.5 million kilometers) from Earth. The radar image in the middle was generated from data collected on Dec. 16 when the asteroid was 2.5 million miles (4.0 million kilometers) from Earth. The image on the right was obtained on Dec. 17 when 2003 SD220 was 2.2 million miles (3.6 million kilometers) from Earth. The spatial resolution on the images is as fine as 12 feet (3.7 meters) per pixel. The radar images reveal the asteroid is at least one mile (1.6 kilometers) long.

Asteroid 2003 SD220 was discovered on Sept. 29, 2003, by astronomers at the Lowell Observatory Near-Earth-Object Search (LONEOS) in Flagstaff, Arizona — an early Near-Earth Object (NEO) survey project supported by NASA that is no longer in operation. The asteroid will fly safely past Earth on Saturday, Dec. 22, 2018, at a distance of about 1.8 million miles (2.9 million kilometers). This will be the asteroid's closest approach in more than 400 years and the closest until 2070, when the asteroid will safely fly by slightly closer.

"Other important applications of gyrotrons are high-power microwave sources include high resolution radar ranging and imaging in atmospheric and planetary science as well as deep-space and specialized satellite communications and RF drivers for next-generation high-gradient linear accelerators".

Clouds
It has a clear eye, but convection is northern part are weak.

Colors
The figure at the right "shows the three-year WMAP spectrum compared to a set of recent balloon and ground-based measurements that were selected to most complement the WMAP data in terms of frequency coverage and l range. The non-WMAP data points are plotted with errors that include both measurement uncertainty and cosmic variance, while the WMAP data in this l range are largely noise dominated, so the effective error is comparable. When the WMAP data are combined with these higher resolution CMB measurements, the existence of a third acoustic peak is well established, as is the onset of Silk damping beyond the 3rd peak."

Theoretical microwave astronomy
Around the year 2000, estimates for the star's age were about 16 billion years. But the universe is about 13.8 billion years old, based on a meticulous calibration of the expansion of space and analysis of the microwave afterglow from the big bang. Hubble data and improved theoretical calculations were used to recalculate the star's age and lower the estimate to 14.5 billion years, within a measurement uncertainty of plus or minus 800 million years. This places the star within a comfortable range to be younger than the universe. Astronomers have to collect a lot of information to deduce a star's age because it doesn't come with a birth certificate. They have to take into account where the star is in its life history, the detailed chemistry of the star, and its intrinsic brightness. Hubble's contribution was to reduce the uncertainty on the star's true distance. With that improved accuracy, the intrinsic brightness of the star is better known. The ancient star is still spry for its age. It is speeding past us at 800,000 miles per hour. Its orbit can be traced back to the halo of our galaxy, which is a "retirement home" for stars that were born long before the Milky Way was even fully assembled.

"Within the WMAP frequency range, it is difficult to distinguish between a primordial CMB spectrum and a thermal SZ [Sunyaev-Zeldovich (SZ) fluctuations] spectrum, so we adopt the Komatsu & Seljak (2002) model for the SZ power spectrum and marginalize over the amplitude as a nuisance parameter."

Entities
Compare the COBE all-sky CMB at right with the map from WMAP in the background section.

"The cosmic microwave background fluctuations are extremely faint, only one part in 100,000 compared to the 2.73 degree Kelvin average temperature of the radiation field."

Electromagnetics
The image above center shows the magnetic field of the Milky Way galaxy via charged particles moving along it.

Weak forces
The Gravity Recovery and Climate Experiment (GRACE) mission uses a microwave ranging system to accurately measure changes in the speed and distance between two identical spacecraft flying in a polar orbit about 220 kilometers (140 mi) apart, 500 kilometers (310 mi) above Earth. The ranging system is sensitive enough to detect separation changes as small as 10 micrometres (approximately one-tenth the width of a human hair) over a distance of 220 kilometers.

As the twin GRACE satellites circle the globe 15 times a day, they sense minute variations in Earth's gravitational pull. When the first satellite passes over a region of slightly stronger gravity, a gravity anomaly, it is pulled slightly ahead of the trailing satellite. This causes the distance between the satellites to increase. The first spacecraft then passes the anomaly, and slows down again; meanwhile the following spacecraft accelerates, then decelerates over the same point.

Emissions
Peryton events are now known to be caused by the emission from a microwave.

The "discovery of the anomalous dust-correlated microwave emission (AME) in the galaxy [was] by Leitch et al (1997) [18] [Characteristics include]
 * 1) the AME constitutes a foreground emission to cosmic microwave background (CMB) radiation. [...]
 * 2) it provides a window into the properties of small grains, which play crucial roles for the physics and chemistry of the ISM.
 * 3) [It is a] diffuse and localized AME"

"In the case of electric dipole radiation, the associated fluctuation in angular momentum is due to absorption of and decays stimulated by microwave photons (dominated by Cosmic Microwave Background (CMB) photons in the diffuse ISM)."

"The [warm ionized medium] WIM is characterized by a large gas temperature T ≈ 8000 K, and a fully ionized gas at low density, nH+ ≈ 0.1 cm-3. Collisions with ions provide the dominant excitation mechanism. Grains are mostly negatively charged due to the high rate of sticking collisions with high-velocity electrons. For a coronene molecule, the characteristic time between ion collisions and the characterstic rotational damping time at the peak angular momentum τrot = √ττed turn out to be comparable6, of order a few years."

The "peak emissivity is enhanced by about 23% for the WIM [and only 11 % for the warm neutral medium (WNM)], although the peak frequency remains unchanged."

"A more important effect on the spectrum is that of increasing the characteristic internal temperature Tω, which makes the grains wobble rather than simply spin about their axis of greatest inertia."

For triaxiality there is an "additional enhancement of the peak frequency and total power by up to the same factors (~ 30 % and 2, respectively) for a large internal relaxation temperature and highly elliptical grains."

Absorptions
"The 111 → 110 rotational transition of formaldehyde (H2CO) [occurs] in absorption in the direction of four dark nebulae. The radiation ... being absorbed appears to be the isotropic microwave background". One of the dark nebulae sampled, per SIMBAD is TGU H1211 P5.

Scatterings
The cosmic microwave background radiation is a faint radio waves glow filling all space radiated at 45,700 million ly - The oldest detectable radiation emitted 380,000 years after the Big Bang - When the universe cooled enough for protons and electrons to combine in neutral hydrogen atoms, the scattering stopped and light was allowed to propagate - Its wavelength has been stretched with space expansion changing its color from orangish-white passing trough infrared and ending in the microwave region of the radio spectrum - Almost isotropic, not associated with any star, galaxy, or another object - Having ruled out that this glow comes from Earth, from local or extended dust or gas, or from distant stars, the CMB is landmark evidence of the Big Bang origin of the universe -.

"Radio waves propagated through the atmosphere are affected by a wide variety of scattering and fading effects due to local anomalies and movements both of neutral and of charged particles."

"Electrons and ions react much more vigorously with radio waves than do neutral species; and electrons, because of their much smaller mass, interact much more vigorously than other ions. Atmospheric radio propagation is, therefore, almost entirely the study of electron-wave-field interactions."

There "is a broad maximum of the rate of absorption of the radio wave; this occurs in the day-time in the standard broadcast band in temperate latitudes and is due to ionization and collision in the D region of the ionosphere."

"At higher frequencies, attenuation decreases with the square of the frequency; the radio wave may be able to pass through the D layer with relatively little absorption and be reflected, with little absorption, in the E or F regions. The least-absorbed frequency is the highest completely reflected from the ionosphere."

"Still higher frequencies may be scattered forward from irregularities in neutral-molecule densities in the troposphere, or in electron densities in the ionosphere. These scattering mechanisms greatly attenuate the forward-scattered radio wave, but these higher frequencies have compensating advantages: less congestion in the radio spectrum and higher directivity achievable with relatively small antennas."

Backgrounds
[B]ackground radiation may simply be any radiation that is pervasive, whether ionizing or not. A particular example of this is the cosmic microwave background radiation, a nearly uniform glow that fills the sky in the microwave part of the spectrum; stars, galaxies and other objects of interest in radio astronomy stand out against this background.

The image at the top shows the "detailed, all-sky picture of the infant universe created from nine years of WMAP data. The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. The signal from the our Galaxy was subtracted using the multi-frequency data. This image shows a temperature range of ± 200 microKelvin."

In the figure at right, CUVOB stands for the cosmic ultraviolet and optical background.

The diffuse extragalactic background light (EBL) is all the accumulated radiation in the Universe due to star formation processes, plus a contribution from active galactic nuclei (AGNs). This radiation covers the wavelength range between ~ 0.1-1000 microns (these are the ultraviolet, optical, and infrared regions of the electromagnetic spectrum). The EBL is part of the diffuse extragalactic background radiation (DEBRA), which by definition covers the overall electromagnetic spectrum. After the cosmic microwave background, the EBL produces the second-most energetic diffuse background, thus being essential for understanding the full energy balance of the universe.

"The observations were made using two arrays of radio telescopes – the Cosmic Background Interferometer (CBI) in Chile and the Very Small Array (VSA) in Tenerife. The experiments have produced the sharpest measurements ever of the temperature variations in the cosmic microwave background. These variations trace the fluctuations in the distribution of primordial matter that seeded the formation of large-scale structure in the universe."

Cosmic rays
Using Chandra, astronomers recently discovered a jet in X-rays being illuminated by the cosmic microwave background. The light from this jet was emitted when the Universe was only one fifth of its present age. The main panel of this graphic shows Chandra's X-ray data combined with an optical image, while the inset focuses on the details of the X-ray emission.

Notation: let the symbol GZK represent Greisen-Zatsepin-Kuzmin.

Based on interactions between cosmic rays and the photons of the cosmic microwave background radiation (CMB) ... cosmic rays with energies over the threshold energy of 5x1019 eV interact with cosmic microwave background photons $$\gamma_{\rm CMB}$$ to produce pions via the $$\Delta$$ resonance,


 * $$\gamma_{\rm CMB}+p\rightarrow\Delta^+\rightarrow p + \pi^0,$$

or


 * $$\gamma_{\rm CMB}+p\rightarrow\Delta^+\rightarrow n + \pi^+.$$

Neutrals
Megamasers are intensely bright, around 100 million times brighter than the masers found in galaxies like the Milky Way. The entire galaxy essentially acts as an astronomical laser that beams out microwave emission rather than visible light (hence the ‘m’ replacing the ‘l’).

A megamaser is a process that involves some components within the galaxy (like gas) that is in the right physical condition to cause the amplification of light (in this case, microwaves). But there are other parts of the galaxy (like stars for example) that aren’t part of the maser process.

This megamaser galaxy is named IRAS 16399-0937 and is located over 370 million light-years from Earth. This NASA/ESA Hubble Space Telescope image belies the galaxy’s energetic nature, instead painting it as a beautiful and serene cosmic rosebud. The image comprises observations captured across various wavelengths by two of Hubble’s instruments: the Advanced Camera for Surveys (ACS), and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

NICMOS’s superb sensitivity, resolution, and field of view gave astronomers the unique opportunity to observe the structure of IRAS 16399-0937 in detail. They found it hosts a double nucleus — the galaxy’s core is thought to be formed of two separate cores in the process of merging. The two components, named IRAS 16399N and IRAS 16399S for the northern and southern parts respectively, sit over 11,000 light-years apart. However, they are both buried deep within the same swirl of cosmic gas and dust and are interacting, giving the galaxy its peculiar structure.

The nuclei are very different. IRAS 16399S appears to be a starburst region, where new stars are forming at an incredible rate. IRAS 16399N, however, is something known as a LINER nucleus (Low Ionization Nuclear Emission Region), which is a region whose emission mostly stems from weakly-ionized or neutral atoms of particular gases. The northern nucleus also hosts a black hole with some 100 million times the mass of the sun!

Pions produced in this manner proceed to decay in the standard pion channels—ultimately to photons for neutral pions, and photons, positrons, and various neutrinos for positive pions. Neutrons decay also to similar products, so that ultimately the energy of any cosmic ray proton is drained off by production of high energy photons plus (in some cases) high energy electron/positron pairs and neutrino pairs.

Protons
Microwaves are fed to the radio frequency (RF) Cavity from the power source (partially visible at the left side in this photo) to accelerate the proton beam.

The pion production process begins at a higher energy than ordinary electron-positron pair production (lepton production) from protons impacting the CMB, which starts at cosmic ray proton energies of only about 1017eV. However, pion production events drain 20% of the energy of a cosmic ray proton as compared with only 0.1% of its energy for electron positron pair production. This factor of 200 is from two sources: the pion has only about ~130 times the mass of the leptons, but the extra energy appears as different kinetic energies of the pion or leptons, and results in relatively more kinetic energy transferred to a heavier product pion, in order to conserve momentum. The much larger total energy losses from pion production result in the pion production process becoming the limiting one to high energy cosmic ray travel, rather than the lower-energy light-lepton production process.

Mesons
The pion production process continues until the cosmic ray energy falls below the pion production threshold. Due to the mean path associated with this interaction, extragalactic cosmic rays traveling over distances larger than 50 Mpc (163 Mly) and with energies greater than this threshold should never be observed on Earth. This distance is also known as GZK horizon.

Beta particles
"The attenuation of photons in the microwave background via the process


 * $$\gamma + \gamma (3^o K) \rightarrow e^+ e^-$$

is strongly energy dependent, with a minimum attenuation length of ≈ 7 kpc around 2.5 PeV, as determined by the threshold for e+e- production (Gould and Schreder, 1966; Jelley, 1966)."

Electrons
It was discovered by the ESA Planck satellite through the Sunyaev-Zel’dovich effect — the distortion of the cosmic microwave background radiation in the direction of the galaxy cluster, by high energy electrons in the intracluster gas. The large galaxy at the centre is the brightest galaxy in the cluster and the dominant object in this image, and above it a thin, curved gravitational lens arc is visible. This is caused by the gravitational forces of the cluster bending the light from stars and galaxies behind it, in a similar way to how a glass lens bends light. Several stars are visible in front of the cluster — recognisable by their diffraction spikes — but aside from these, all other visible objects are distant galaxies. Their light has become redshifted by the expansion of space, making them appear redder than they actually are. By measuring the amount of redshift, we know that it took more than 5 billion years for the light from this galaxy cluster to reach us. The light of the galaxies in the background had to travel for even longer than that, making this image an extremely old window into the far reaches of the Universe. This image was taken by Hubble’s Advanced Camera for Surveys (ACS) and Wide-Field Camera 3 (WFC3) as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

A "PeV energy photon cannot deliver information from a source at the edge of our own galaxy because it will annihilate into an electron [positron] pair in an encounter with a 2.7 Kelvin microwave photon before reaching our telescope."

"In general, energetic photons above a threshold E given by


 * $$4E\epsilon \sim (2m_e)^2,$$

where E and ε are the energy of the high-energy and background photon, respectively. [This] implies that TeV-photons are absorbed on infrared light, PeV photons on the cosmic microwave background and EeV photons on radio-waves".

"Each [optical module] OM contains a 10 inch [photo-multiplier tube] PMT that detects individual photons of Cerenkov light generated in the optically clear ice by muons and electrons moving with velocities near the speed of light."

"Radio Cerenkov experiments detect the Giga-Hertz pulse radiated by shower electrons produced in the interaction of neutrinos in ice."

"Above a threshold of ≃ 1PeV, the large number of low energy(≃ MeV ) photons in a shower will produce an excess of electrons over positrons by removing electrons from atoms by Compton scattering. These are the sources of coherent radiation at radio frequencies, i.e. above ∼ 100MHz."

Gamma rays
High-energy gamma rays detected by Fermi's Large Area Telescope are depicted as purple in this gamma ray/optical composite of the galaxy.

Gamma-ray bursts (GRBs) are flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the most luminous electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several minutes, although a typical burst lasts 20–40 seconds. The initial burst is usually followed by a longer-lived "afterglow" emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and radio).

X-rays
The jet is likely due to the collision of a beam of high-energy electrons with microwave photons. Image is 60 arcsec on a side. RA 11h 30m 7.10s | Dec -14° 49' 27" in Crater. Observation date: May 28, 2000. Instrument: ACIS.

Ultraviolets
As can be easily seen, UGC 6093 is something known as a barred spiral galaxy — it has beautiful arms that swirl outwards from a bar slicing through the galaxy’s center. It is classified as an active galaxy, which means that it hosts an active galactic nucleus, or AGN: a compact region at a galaxy’s center within which material is dragged towards a supermassive black hole. As this black hole devours the surrounding matter it emits intense radiation, causing it to shine brightly. But UGC 6093 is more exotic still. The galaxy essentially acts as a giant astronomical laser that spews out light at microwave, not visible, wavelengths — this type of object is dubbed a megamaser (maser being the term for a microwave laser). Megamasers such as UGC 6093 can be some 100 million times brighter than masers found in galaxies like the Milky Way. Hubble’s WFC3 observes light spanning a range wavelengths — from the near-infrared, through the visible range, to the near-ultraviolet. It has two channels that detect and process different light, allowing astronomers to study a remarkable range of astrophysical phenomena; for example, the UV-visible channel can study galaxies undergoing massive star formation, while the near-infrared channel can study redshifted light from galaxies in the distant Universe. Such multi-band imaging makes Hubble invaluable in studying megamaser galaxies, as it is able to untangle their intriguing complexity.

Opticals
This false-color image shows tiny variations in the intensity of the cosmic microwave background measured in four years of observations by the Differential Microwave Radiometers on NASA's Cosmic Background Explorer (COBE). The cosmic microwave background is widely believed to be a remnant of the Big Bang; the blue and red spots correspond to regions of greater or lesser density in the early Universe. These "fossilized" relics record the distribution of matter and energy in the early Universe before the matter became organized into stars and galaxies. While the initial discovery of variations in the intensity of the CMB (made by COBE in 1992) was based on a mathematical examination of the data, the new picture of the sky from the full four-year mission gives an accurate visual impression of the data. The features traced in this map stretch across the visible Universe: the largest features seen by optical telescopes, such as the "Great Wall" of galaxies, would fit neatly within the smallest feature in this map.

Visuals
This galaxy has two particularly striking features: a beautiful dust lane and an intensely bright centre — much brighter than that of our own galaxy, or indeed those of most spiral galaxies we observe.

NGC 5793 is a Seyfert galaxy. These galaxies have incredibly luminous centres that are thought to be caused by hungry supermassive black holes — black holes that can be billions of times the size of the Sun — that pull in and devour gas and dust from their surroundings.

This galaxy is of great interest to astronomers for many reasons. For one, it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation [1]. Naturally occurring masers, like those observed in NGC 5793, can tell us a lot about their environment; we see these kinds of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, which are thousands of times more luminous than the Sun.

Blues
From 2009 to 2013, the ESA Planck satellite mapped the Cosmic Microwave Background (CMB) in unprecedented detail. The CMB represents our most ancient view of the universe, since it represents the era in which space first became transparent to radiation after the Big Bang. This image was created by running the entire CMB map through a Mean Curvature Diffusion filter for noise removal, after which the entropy of each image plane (Red, Green, Blue) was independently computed. The image was created using the Rapid EXploitation [REX] image processing system on LINUX/Windows-10, distributed by imagtek.com.

Cyans
This antihydrogen experiment features three sections (a, b, and c): a, Central parts of the ALPHA-2 apparatus are schematically shown. The field for the magnetic minimum trap is produced by five mirror coils for longitudinal confinement and one octupole coil for transverse confinement. The trap has a depth of about 50 μeV with an axial length of 280 mm and a diameter of 44.35 mm. The magnetic trap is superimposed on a cryogenic Penning trap (the electrodes are shown in yellow). An external solenoid, not shown, provides a 1-T base field for charged particle trapping and cooling. The solenoids at either end of the trap further boost the field in the preparation traps to 3 T for more efficient cyclotron cooling of electrons, positrons (e+) and antiprotons (p¯), before antihydrogen synthesis. The atom trap is surrounded by a silicon vertex annihilation detector made of three layers of double-sided microstrip sensors. The pulsed Lyman-α light at 121.6 nm, generated in a gas cell immediately outside the ultrahigh vacuum chamber, is introduced through a magnesium fluoride window with an angle of 2.3° with respect to the trap axis to allow particle loading on axis into the Penning trap. The intensity of the 121.6-nm pulse is recorded by a solar-blind photomultiplier (PMT) placed after the trap. A cryogenic optical cavity serves to both build up the 243.1-nm laser light needed to drive the 1S–2S transitions, and to provide the counter-propagating photons that cancel the first-order Doppler shift. Microwaves, used to drive hyperfine transitions, and to perform electron cyclotron resonance magnetometry, are injected through the microwave guide. According to the coordinate system shown, we define the longitudinal kinetic energy to be 1/2mHv2z, and the transverse one to be 1/2mH (vx2+vy2), where mH is the mass of antihydrogen, and vx, vy and vz are the velocity components in the x, y and z directions. b, Magnetic field profile on the axis of the trap. The shaded region illustrates a volume in which the field on axis is uniform to 0.01 T, corresponding to a Zeeman shift of 140 MHz in the 1S–2Pa transition. Immediately before reach run, the magnetic field at the centre of the trap was measured via electron cyclotron resonance and the laser frequencies were adjusted accordingly. The measured magnetic minimum field, averaged over the pre-run measurements, was 1.03270 ± 0.00007 T, where the error is the standard deviation from the set of measurements. c, The energy levels of the antihydrogen in the n = 1 and n = 2 states are depicted as a function of the magnetic field. On the vertical axis, the centroid energy difference, E1S–2S = 2.4661 × 1015 Hz, has been suppressed. The dotted vertical black line represents the field at the magnetic minimum of our trap, 1.0327 T (see above). Details of the energy levels near this field and their state labels are shown on the right of the figure. The first value in the ket notation represents the quantum number of the projection of the total angular momentum of the positron, mL + mS, where L is the orbital angular momentum (L = 0 for the S state and L = 1 for the P state, respectively) and S is the spin (S = 1/2). The double arrow shows the antiproton spin (up or down). Initially, both the 1Sc and 1Sd states are trapped in our magnetic trap. The grey arrow indicates the microwave-driven 1Sc → 1Sb transition to eliminate the anti-atoms in the 1Sc hyperfine state and prepare a doubly spin-polarized antihydrogen sample in the 1Sd state. The solid and broken red (cyan) arrows indicate the cycling transition for laser cooling (heating) with red (blue) detuning −δ (+δ′). The purple arrow represents the probe laser excitation to the 2Pc– level. Note that the 2Pc state at a magnetic field of about 1 T is a superposition of the positron spin-up (mL = 0, mS = +1/2) and spin-down (mL = +1, mS = –1/2) states. Owing to this superposition, upon de-excitation from the 2Pc state, the anti-atom can either go back to the original 1Sd state, or undergo an effective ‘spin flip’ transition to the 1Sa state. In the latter case, the anti-atom is forced out of the trap and detected via its annihilation signal. The black arrows show the two-photon excitation from the 1Sd state to the 2Sd state.

Greens
The crater rim is seen in the upper center of the image as a radar-bright, circular feature. Geologists believe the crater was formed by a meteorite that collided with Earth approximately 5 million years ago. The data were acquired by the Spaceborne Imaging Radar- C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) instrument onboard space shuttle Endeavour on April 14, 1994.

The colors in this image were obtained using the following radar channels: red represents the L-band (horizontally transmitted and received); green represents the L-band (horizontally transmitted and vertically received); and blue represents the C-band (horizontally transmitted and vertically received). The area shown is approximately 25.5 kilometers (15.8 miles) by 36.4 kilometers (22.5 miles), with north toward the upper left. The bright white irregular feature in the upper right corner is a small hill of exposed rock outcrop. Roter Kamm is a moderate sized impact crater, 2.5 kilometers (1.5 miles) in diameter rim to rim, and is 130 meters (400 feet) deep. However, its original floor is covered by sand deposits at least 100 meters (300 feet) thick. In a conventional aerial photograph, the brightly colored surfaces immediately surrounding the crater cannot be seen because they are covered by sand. The faint blue surfaces adjacent to the rim may indicate the presence of a layer of rocks ejected from the crater during the impact. The darkest areas are thick windblown sand deposits which form dunes and sand sheets. The sand surface is smooth relative to the surrounding granite and limestone rock outcrops and appears dark in radar image. The green tones are related primarily to larger vegetation growing on sand soil, and the reddish tones are associated with thinly mantled limestone outcrops.

Reds
As well as this microwave emission from Messier 106’s heart, the galaxy has another startling feature - instead of two spiral arms, it appears to have four. Although the second pair of arms can be seen in visible light images as ghostly wisps of gas, as in this image, they are even more prominent in observations made outside of the visible spectrum, such as those using X-ray or radio waves.

Unlike the normal arms, these two extra arms are made up of hot gas rather than stars, and their origin remained unexplained until recently. Astronomers think that these, like the microwave emission from the galactic centre, are caused by the black hole at Messier 106’s heart, and so are a totally different phenomenon from the galaxy’s normal, star-filled arms.

The extra arms appear to be an indirect result of jets of material produced by the violent churning of matter around the black hole. As these jets travel through the galactic matter they disrupt and heat up the surrounding gas, which in turn excites the denser gas in the galactic plane and causes it to glow brightly. This denser gas closer to the centre of the galaxy is tightly-bound, and so the arms appear to be straight. However, the looser disc gas further out is blown above or below the disc in the opposite direction from the jet, so that the gas curves out of the disc — producing the arching red arms seen here.

Colours & filters: Band	Wavelength	Telescope Infrared I	814 nm	Hubble Space Telescope ACS Infrared I	814 nm	Hubble Space Telescope WFC3 Optical H-alpha	656 nm	Hubble Space Telescope WFPC2 Optical V	555 nm	Hubble Space Telescope ACS Optical V	606 nm	Hubble Space Telescope ACS Optical V	555 nm	Hubble Space Telescope WFC3 Optical B	435 nm	Hubble Space Telescope ACS

M106 has a water vapor megamaser (the equivalent of a laser operating in microwave instead of visible light and on a galactic scale) that is seen by the 22-GHz line of ortho-H2O that evidences dense and warm molecular gas that give M106 its characteristic purple color. Water masers are useful to observe nuclear accretion disks in active galaxies, enabling the first case of a direct measurement of the distance to a galaxy, thereby providing an independent anchor for the cosmic distance ladder. M106 has a slightly warped, thin, almost edge-on Keplerian disc which is on a subparsec scale that surrounds a central area with mass 4 × 107 M⊙.

Infrareds
Intense hurricanes can and often undergo an eyewall replacement cycle. That happens when a new eyewall or ring of thunderstorms within the outer rain bands forms further out from the storm's center, outside of the original eye wall. That ring of thunderstorms then begins to choke off the original eye wall, starving it of moisture and momentum. Eventually, if the cycle is completed, the original eye wall of thunderstorms dissipates and the new outer eye wall of thunderstorms contracts and replace the old eye wall. The storm's intensity can fluctuate over this period, initially weakening as the inner eye wall dies before again strengthening as the outer eye wall contracts.

Infrared and Microwave Satellite Images Reveal NOAA's National Hurricane Center (NHC) said that recent satellite imagery shows that the eye of Florence has become cloud filled. A microwave image of the storm at 12:41 a.m. EDT (0441 UTC) showed a double eyewall structure. These observations suggest that an eyewall replacement cycle is likely underway.

At 2:30 a.m. EDT (0630 UTC) on Sept. 11, Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA's Aqua satellite analyzed Hurricane Florence in infrared light. MODIS found coldest cloud top temperatures around the eye, as cold as or colder than minus 80 degrees (yellow) Fahrenheit (F)/minus 112 degrees Celsius (C). Surrounding the eye were thick rings of powerful storms with cloud tops as cold as or colder than minus 70F (red) (minus 56.6C).

NASA research has found that cloud top temperatures as cold as or colder than the 70F/56.6C threshold have the capability to generate heavy rainfall.

Submillimeters
Data from ALMA’s 7- and 12-metre antennas has been combined to produce the sharpest possible image. The target was one of the most massive known galaxy clusters, RX J1347.5–1145, the centre of which shows up here in the dark “hole” in the ALMA observations. The energy distribution of the [cosmic microwave background] CMB photons shifts and appears as a temperature decrease at the wavelength observed by ALMA, hence a dark patch is observed in this image at the location of the cluster.

Submillimetre astronomy or submillimeter astronomy is the branch of observational astronomy that is conducted at submillimetre wavelengths of the electromagnetic spectrum. Astronomers place the submillimetre waveband between the far-infrared and microwave wavebands, typically taken to be between a few hundred micrometres and a millimetre. Using submillimetre observations, astronomers examine molecular clouds and dark cloud cores with a goal of clarifying the process of star formation from earliest collapse to stellar birth.

Radars
The image is centered at 46.82 degrees north latitude and 10.79 degrees east longitude. This image is located in the Central Alps at the border between Switzerland, Italy and Austria, 50 kilometers (31 miles) southwest of Innsbruck. It was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture aboard the space shuttle Endeavour on April 14, 1994 (STS-62 crew) and on October 5, 1994 (STS-65 crew). It was produced by combining data from these two different data sets. Data obtained in April is green; data obtained in October appears in red and blue, and was used as an enhancement based on the ratio of the two data sets. Areas with a decrease in backscatter from April to October appear in light blue (cyan), such as the large Gepatschferner glacier seen at the left of the image center, and most of the other glaciers in this view. A light blue hue is also visible at the east border of the dark blue Lake Reschensee at the upper left side. This shows a significant rise in the water level. Magenta represents areas with an increase of backscatter from April 10 to October 5. Yellow indicates areas with high radar signal response during both passes, such as the mountain slopes facing the radar. Low radar backscatter signals refer to smooth surface (lakes) or radar grazing areas to radar shadow areas, seen in the southeast slopes. The area is approximately 29 kilometers by 21 kilometers (18 miles by 13.5 miles). The summit of the main peaks reaches elevations of 3,500 to 3,768 meters (xx feet to xx feet) above sea level. The test site's core area is the glacier region of Venter Valley, which is one of the most intensively studied areas for glacier research in the world. Research in Venter Valley (below center) includes studies of glacier dynamics, glacier-climate regions, snowpack conditions and glacier hydrology. About 25 percent of the core test site is covered by glaciers. Corner reflectors are set up for calibration.

Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/ X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The SIR-C/X-SAR data is to be complemented by aircraft and ground studies.

Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the echoes. This research has been conducted for six decades. Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an active one. Radar systems have been used for a wide range of solar system studies. The radar transmission may either be pulsed or continuous.

Radios
The black lines show the simulated spectrum (in brightness temperatures TB) for a ground-based receiver; the colored lines are the spectrum obtained from a satellite instrument over the ocean measuring at horizontal (blue) and vertical (red) linear polarization. Solid lines indicate simulations for clear-sky (cloud-free) conditions, dotted lines show a clear-sky case with a single layer liquid cloud.

A radiometer or roentgenometer is a device for measuring the radiant flux (power) of electromagnetic radiation such as infrared radiation detector or an ultraviolet detector.

Several satellites have served as observatories for radio waves and specifically for microwaves. The Radio Astronomy Explorer (RAE) 1 was launched into orbit on July 4, 1968, around Earth, while the [Explorer 49] RAE 2 was launched on June 10, 1973, around the Moon.

The COBE was launched into Earth orbit on November 18, 1989. The WMAP was launched on June 30, 2001, into orbit at the [Lissajous orbit] Lagrange 2 location. Both satellites have aboard detectors designed to perform microwave astronomy, as these are limited to only the microwave band.

Superluminals
"We propose a method for estimating the composition, i.e. the relative amounts of leptons and protons, of extragalactic jets which exhibit X-ray bright knots in their kpc scale jets. The method relies on measuring, or setting upper limits on, the component of the Cosmic Microwave Background (CMB) radiation that is bulk-Comptonized by cold electrons in the relativistically flowing jet. These measurements, along with modeling of the broadband knot emission that constrain the bulk Lorentz factor Γ of the jets, can yield estimates of the jet power carried by protons and leptons. We provide an explicit calculation of the spectrum of the bulk-Comptonized (BC) CMB component and apply these results to PKS 0637–752 and 3C 273, two superluminal quasars with Chandra – detected large scale jets."

Plasma objects
A plasma object may be simply an object consisting of mobile charged particles. The percentage of neutral particles is often ignored.

Gaseous objects
This new Hubble image is centered on NGC 5793, a spiral galaxy over 150 million light-years away in the constellation of Libra. This galaxy has two particularly striking features: a beautiful dust lane and an intensely bright center — much brighter than that of our own galaxy, or indeed those of most spiral galaxies we observe.

This galaxy is of great interest for many reasons: it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation. The term "masers" comes from the acronym Microwave Amplification by Stimulated Emission of Radiation. Maser emission is caused by particles that absorb energy from their surroundings and then re-emit this in the microwave part of the spectrum. Naturally occurring masers, like those observed in NGC 5793, can tell us a lot about their environment; we see these kinds of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, which are thousands of times more luminous than the sun.

Liquid objects
"Passive microwave satellite observations [in the image on the right] indicate that surface melt occurred during one or more days over a broad sector of West Antarctica (termed Ross sector hereafter) in January 2016, with up to 15 melt days over parts of the eastern Ross Ice Shelf and Siple Coast."

"January 2016 was one of the three largest melt events in the Ross sector since 1978 (second behind 1991–92 for [melt index (MI) (melt area weighted by duration of the melting)] MI, and a virtual tie for first with January 2005 for melt extent)."

"The satellite observations were corroborated on the ground by a number of automatic weather stations (AWSs) that recorded near-surface temperatures near or above 0 °C for several consecutive days during 10–21 January [...]. The onset of the melt event on 10 January was accompanied by an abrupt temperature increase at WAIS Divide and Byrd, in central West Antarctica. The temperature time series from these two sites highlight roughly two phases: Phase 1 (10–14 January), during which the temperatures were at their warmest; and Phase 2 (15–21 January), during which the temperatures gradually decreased towards their pre-event levels. The transition from Phase 1 to Phase 2 is characterized by a shift of the melt pattern towards the Transantarctic Mountains apparent in the AWS temperature time series and in the sequence of daily melt maps [...]."

"[R]ain was witnessed by a field party on 12 January (Dr Huw Horgan, Victoria University of Wellington, personal communication)."

Rocky objects
The Askaryan effect is the phenomenon whereby a particle traveling faster than the phase velocity of light in a dense dielectric (such as salt, ice or the lunar regolith) produces a shower of secondary charged particles which contain a charge anisotropy and thus emits a cone of coherent radiation in the radio or microwave part of the electromagnetic spectrum. It is similar to the Cherenkov effect.

"The red [image at center shows] the heat coming from dust throughout the Milky Way galaxy. Planck can capture this thermal light even though the dust is extremely cold — about minus 420 Fahrenheit (minus 251 Celsius)."

Astrochemistry
"The detection of interstellar formaldehyde provides important information about the chemical physics of our galaxy. We now know that polyatomic molecules containing at least two atoms other than hydrogen can form in the interstellar medium." "H2CO is the first organic polyatomic molecule ever detected in the interstellar medium".

Hydrogens
The hydrogen line, 21 centimeter line or HI line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420.40575177 [megahertz] MHz, which is equivalent to the vacuum wavelength of 21.10611405413 cm in free space. This wavelength or frequency falls within the microwave radio region of the electromagnetic spectrum, and it is observed frequently in radio astronomy, since those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light.

Ions
Charged particle interactions around the galaxy are shown in the image above using microwaves as detected by the Planck satellite.

Molecules
"This all-sky image [above center] shows the distribution of carbon monoxide (CO), a molecule used by astronomers to trace molecular clouds across the sky, as seen by Planck."

Compounds
So far the effect has been observed in silica sand, rock salt, and ice.

Atmospheres
At the right is a plot of the zenith atmospheric microwave transmission on the summit of Mauna Kea, Earth, in the gigahertz range at a precipitable water vapor level of 0.001 mm.

Spectrometers
[C]osmic microwave background (CMB) radiation (also CMBR, CBR, MBR, and relic radiation) is thermal radiation filling the observable universe almost uniformly.

Precise measurements of cosmic background radiation are critical to cosmology, since any proposed model of the universe must explain this radiation. The CMBR has a thermal black body spectrum at a temperature of 2.725 K, which peaks at the microwave range frequency of 160.2 GHz, corresponding to a 1.873 mm wavelength. This holds if measured per unit frequency, as in Planck's law. If measured instead per unit wavelength, using Wien's law, the peak is at 1.06 mm corresponding to a frequency of 283 GHz.

"The differential 850-μm counts are well described by the function


 * $$n(S) = N_0/(a + S^{3.2}),$$

where $$S$$ is the flux in mJy, $$N_0$$ = 3.0 × 104 per square degree per mJy, and $$a$$ = 0.4 − 1.0 is chosen to match the 850-μm extragalactic background light."

Sun
At right is a radio image of the Sun at 4.6 GHz. "The brightest discrete radio source is the Sun, but it is much less dominant than it is in visible light. The radio sky is always dark, even when the Sun is up, because atmospheric dust doesn't scatter radio waves, whose wavelengths are much longer than the dust particles."

"The quiet Sun at 4.6 GHz imaged by the [Very Large Array] VLA with a resolution of 12 arcsec, or about 8400 km on the surface of the Sun. The brightest features (red) in this false-color image have brightness temperatures ~ 106 K and coincide with sunspots. The green features are cooler and show where the Sun's atmosphere is very dense. At this frequency the radio-emitting surface of the Sun has an average temperature of 3 x 104 K, and the dark blue features are cooler yet. The blue slash crossing the bottom of the disk is a feature called a filament channel, where the Sun's atmosphere is very thin: it marks the boundary of the South Pole of the Sun. The radio Sun is somewhat bigger than the optical Sun: the solar limb (the edge of the disk) in this image is about 20000 km above the optical limb."

"The microwave radiation from the sun was observed during the partial eclipse of July 9, 1945."

Earth
This image is based on data gathered by the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) on NASA’s Aqua satellite.

Arctic Sea Ices
Sea ice extent maps are derived from data captured by the Scanning Multichannel Microwave Radiometer aboard NASA's Nimbus-7 satellite and the Special Sensor Microwave Imager on multiple satellites from the Defense Meteorological Satellite Program.

The frozen cap of the Arctic Ocean appears to have reached its annual summertime minimum extent and broken a new record low on Sept. 16, the National Snow and Ice Data Center (NSIDC) has reported. Analysis of satellite data by NASA and the NASA-supported NSIDC at the University of Colorado in Boulder showed that the sea ice extent shrunk to 1.32 million square miles (3.41 million square kilometers).

The new record minimum measures almost 300,000 square miles less than the previous lowest extent in the satellite record, set in mid-September 2007, of 1.61 million square miles (4.17 million square kilometers). For comparison, the state of Texas measures around 268,600 square miles.

Craters
Data acquired on April 13, 1994 and on October 4, 1994 from the X-band Synthetic Aperture Radar on board the space shuttle Endeavour were used to generate interferometric fringes, which were overlaid on the X-SAR image of Kilauea. The volcano is centered in this image at 19.58 degrees north latitude and 155.55 degrees west longitude. The image covers about 9 kilometers by 13 kilometers (5.6 miles by 8 miles). The X-band fringes correspond clearly to the expected topographic image. The yellow line indicates the area below which was used for the three-dimensional image using altitude lines. The yellow rectangular frame fences the area for the final topographic image.

"In the winter of 1931 Karl G. Jansky1 of the Bell Telephone Laboratoies was making studies of the direction of arrival of high-frequency atmospheric static with a radio receiver tuned to a frequency of 20.5 x 106 cycles/sec. He discovered a faint source of static whose direction slowly changed throughout the day, and had approximately the same direction every day at the same time. He began an intensive study of this phenomenon, and determined that the variation of azimuth of the unknown source coincided with that of the sun. He continued his observations over a period of several months, and found that as the sun moved eastward, the direction from which the signal was coming remained fixed on the celestial sphere.2 By an ingenious method he determined its approximate right ascension and declination, and showed that they coincided roughly with the direction in which astronomers placed the centre of our galactic system. His papers contain the first published evidence for the existence of extra-terrestrial radiation at radio-frequencies."

"Jansky's observations dramatically opened up the new "microwave region" -- a whole new section of the electromagnetic spectrum to which the earth's atmosphere is transparent. […] The microwave region is limited on the high frequency side by the absorptions of various molecules in the atmosphere, and on the low frequency side by the ionosphere, which absorbs or reflects electromagnetic vibrations of frequencies lower than a critical value."

"[E]xtra-terrestrial microwave radiation has been detected from four sources:
 * 1) The Milky Way emits radiation in frequencies between 20 mc./sec and 480 mc./sec.
 * 2) The sun has measurable radiation between the limits of 20 mc./sec. and 30,000 mc./sec.
 * 3) The moon6 at full phase radiates at 24,000 mc./sec., as though it were at a temperature near 0°C.
 * 4) The Andromeda nebula7 (the nearest galaxy comparable in size with our own) gives faint indications of radiation at 162 mc./sec. Most observers have reported negative results from the planets and some of the brighter stars."

Greenland ice sheets
"Active and passive microwave satellite data are used to map snowmelt extent and duration on the Greenland ice sheet. The passive microwave (PM) data reveal the extreme melt extent of 690,000 km2 in 2002 as compared with an average extent of 455,000 km2 from 1979–2003."

"Several PM-based melt assessment algorithms [Mote and Anderson, 1995; Abdalati and Steffen, 1995] are applicable to Scanning Multi-channel, Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) instruments providing near-continuous coverage since 1979. The PM data as gridded brightness temperatures on polar stereographic grids (25 km resolution) [used] are from the National Snow and Ice Data Center [Maslanik and Stroeve, 2003], containing daily data spanning 25 melt seasons from 1979 to 2003."

In the image at the right, (a) "shows the probabilities of the observed melt behavior on the Greenland ice sheet for several large melt years and indicates the extreme melt anomaly observed in northeastern Greenland in 2002."

"Prior to 2002, both 1995 and 1998 were extreme melt years in terms of maximum areal extent and total melt. During 1995 melt was dominated by a high frequency of melt along the western margin of the ice sheet. During 1998 melt was spatially diverse with slightly more melt than usual in the northeast and southwest. However, the high frequency melt in 2002 in the northeast and along the western margin is unprecedented in the PM record with a log likelihood of occurrence that is 35% lower than the previous record melt anomaly in 1991."

(c) "depicts the magnitude of the increasing trends in melt extent on a daily basis over the last 25 years. Although there is a large amount of inter-annual variability in melt extent on a given day, 56 days show statistically significant (alpha = 0.1) increasing trends in melt area."

"Melt along the west coast was extensive during 2002 but not atypical for large melt years. However melt in the north and northeast was highly irregular both in terms of extent and frequency. Nearly 3,000 km2[(b)] were classified as melting during 2002 that had not previously melted during any other year between 1979 and 2003."

The figure at the left "presents QSCAT backscatter and diurnal signatures, and ETH/CU AWS air temperature." Half-decade records for ETH/CU Camp station: (a) Top panel is for QSCAT backscatter, (b) middle panel for QSCAT diurnal signature, and (c) bottom panel for air temperature measured at the AWS site.

At the lower right QSCAT melt maps are shown on the climatological peak-melt day (1 August). Red color represents current active melt areas, light blue is for areas that have melted but currently refreeze, white is for areas that will melt later, and magenta is for areas that do not experience any melt throughout the melt season. The dark blue color surrounding Greenland is the ocean mask.

"QSCAT mapping can reveal details of the spatial pattern of surface melt evolution in time. There are large variabilities in melt extent and melt timing over different regions. [The figure at tje lower right] confirms that 2002 has the most extensive areal melt. In 2002, the northeast quadrant of the Greenland ice sheet, extending well into the dry snow zone, experienced at least some melt where melt never happened before (from satellite data records to date). Since the beginning of the QSCAT data record (July 1999), the smallest spatial extent of melt occurred in 2001, and melt extent was similar for years 2000 and 2003."

"To provide a direct comparison of PM and QSCAT results, we overlay results for PM melt extent and QSCAT number of melt days in [the figure at the lower left] for years 2000–2003. PM XPGR melt extent is approximately confined to QSCAT melt areas experiencing 2 weeks or more of melting time [the figure at the lower left]. QSCAT melt areas outside of the PM melt extent represent the surface that has less melt corresponding to about 15 melt days or less. This is consistent with the relationship of relative melt strength measured by active and passive data as discussed above. Note that such areas can total up to a large region in year 2002. Surface albedo can reduce considerably once the snow melts for a period of 2 weeks. The albedo reduction may significantly impact the surface heat balance and thus change the mass balance. The large number of melt days around the northern perimeter of the ice sheet, which is shown as the narrow dark-red band in north Greenland in the 2003 map was an anomalous feature [the figure at the lower left]. This band was wider as defined by the PM melt extent in 2002 than in 2003. However, there were more QSCAT melt days in the 2003 northern melt band."

"The comparison reveals that the PM cross-polarized gradient algorithm classifies melt more conservatively than the scatterometer algorithm. The active microwave identifies melt approximately up to two weeks more than the PM at higher elevation in the percolation zone toward the dry snow zone [the figure at the lower left]. Both methods (active and passive microwave) consistently identify melt areas that have a melt duration of at least 10–14 days. The longer snowmelt duration can be sufficient to decrease surface albedo and affect surface heat and mass balance."

Hurricanes
Every area in yellow, orange or red represents 82 degrees Fahrenheit or above. SSTs at or above 82 degrees will allow hurricanes to strengthen. The data came from the Advanced Microwave Scanning Radiometer (AMSR-E) instrument on NASA's Aqua satellite.

Polarizations
Location: Traunstein, Germany, Time: 5 November 2007, 12:39-12:41 (UTC), Instrument: F-SAR Platform: Aircraft (Dornier Do228-212), Wavelength: 3 cm (X-Band), Polarisation: HH-HV-VV, (red-green-blue), Image Content: Radar reflectivity in three polarisations, Image Geometry: Slant range projected to ground (ground range), Image Size: 4278 x 6187 (cutout from original image), Pixel Size: 34.2cm x 29.9cm (flight direction x slant range), Resolution: 1.00m x 0.60m, looks: 8 x 1.

Rainfalls
The highest rainfall totals during tropical storm Barry were on the order of 100–150 millimeters (4–6 inches). These areas of heavy rain over south-central Florida and east-central Georgia are marked in red. Lesser amounts of rain, on the order of 50 to 75 millimeters (2–3 inches; green to yellow areas), fell over most of peninsular Florida, the eastern half of Georgia and North and South Carolina. Despite the beneficial rains, most of the area remained in a drought.

The rainfall measurements shown here are from the Multi-satellite Precipitation Analysis, which is based on measurements taken by the Tropical Rainfall Measuring Mission satellite (TRMM). TRMM provides valuable images and information on tropical cyclones around the tropics using a combination of passive microwave and active radar sensors, including the first precipitation radar in space. TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Salinity
Its rich tapestry of global salinity patterns demonstrates Aquarius' ability to resolve large-scale salinity distribution features clearly and with sharp contrast. The map provides a much better picture of ocean surface salinity than the Aquarius science team expected to have this early in the mission.

The new map is a composite of the first two and a half weeks of data since Aquarius became operational on August 25. The numerical values represent salt concentration in parts per thousand (grams of salt per kilogram of sea water). Yellow and red colors represent areas of higher salinity, with blues and purples indicating areas of lower salinity. Areas colored black are gaps in the data. The average salinity on the map is about 35.

The map reveals predominantly well-known ocean salinity features, such as higher salinity in the subtropics, higher average salinity in the Atlantic Ocean compared to the Pacific and Indian Oceans, and lower salinity in rainy belts near the equator, in the northernmost Pacific Ocean and elsewhere. These features are related to large-scale patterns of rainfall and evaporation over the ocean, river outflow and ocean circulation. Aquarius will monitor how these features change over time and study their link to climate and weather variations.

Other important regional features are clearly evident, including a sharp contrast between the arid, high-salinity Arabian Sea west of the Indian subcontinent, and the low-salinity Bay of Bengal to the east, which is dominated by the Ganges River and south Asia monsoon rains. The data also show important smaller details, such as a larger-than-expected extent of low-salinity water associated with outflow from the Amazon River.

To produce the map, Aquarius scientists performed a preliminary calibration of the early data gathered by comparing them with ocean surface salinity reference data. These early data contain some uncertainties, and months of additional calibration and data validation work remain. For example, measurements in the southernmost ocean regions are not yet reliable as they have large uncertainties associated with high winds and low surface temperatures. The north-south striped patterns visible throughout the image are artifacts of small residual calibration errors and are not real. In addition, low salinity values immediately adjacent to land and ice-covered areas are due to proximity to coastlines or ice edges, which introduces errors into the data that will require additional analyses to correct.

Aquarius is making NASA's first space observations of ocean surface salinity variations, a key component of Earth's climate that is linked to the cycling of freshwater around our planet and that influences ocean circulation. The Aquarius/SAC-D (Satélite de Aplicaciones Cientí­ficas) observatory is a collaboration between NASA and Argentina's space agency, Comisión Nacional de Actividades Espaciales (CONAE). The mission launched June 10, 2011, from California's Vandenberg Air Force Base.

Temperatures
The top image shows temperatures in the middle troposphere, centred around 5 kilometres above the surface. The lower image shows temperatures in the lower stratosphere, centred around 18 kilometres above the surface. Oranges and yellows dominate the troposphere image, indicating that the air nearest the Earth’s surface warmed during the period. The stratosphere image is dominated by blues and greens, indicating cooling.

Image was created using data provided courtesy of Remote Sensing Systems. The measurements were taken by Microwave Sounding Units and Advanced Microwave Sounding Units flying on a series of National Oceanic and Atmospheric Administration (NOAA) weather satellites.

Moon
"On October 19, 1945, at 10:25 P.M., E.S.T., the effective black-body temperature of the nearly full moon was measured to be 292° K."

"Very precise microwave measurements between two spacecraft, named Ebb and Flow, were used to map gravity with high precision and high spatial resolution. The field shown resolves blocks on the surface of about 12 miles (20 kilometres) and measurements are three to five orders of magnitude improved over previous data. Red corresponds to mass excesses and blue corresponds to mass deficiencies. The map shows more small-scale detail on the far side of the moon compared to the nearside because the far side has many more small craters."

"Twin NASA probes orbiting Earth's moon have generated the highest resolution gravity field map of any celestial body. The new map, created by the Gravity Recovery and Interior Laboratory (GRAIL) mission, is allowing scientists to learn about the moon's internal structure and composition in unprecedented detail. Data from the two washing machine-sized spacecraft also will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved."

"The gravity field map reveals an abundance of features never before seen in detail, such as tectonic structures, volcanic landforms, basin rings, crater central peaks and numerous simple, bowl-shaped craters. Data also show the moon's gravity field is unlike that of any terrestrial planet in our solar system."

""What this map tells us is that more than any other celestial body we know of, the moon wears its gravity field on its sleeve," said GRAIL Principal Investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "When we see a notable change in the gravity field, we can sync up this change with surface topography features such as craters, rilles or mountains.""

"According to Zuber, the moon's gravity field preserves the record of impact bombardment that characterized all terrestrial planetary bodies and reveals evidence for fracturing of the interior extending to the deep crust and possibly the mantle. This impact record is preserved, and now precisely measured, on the moon. The probes revealed the bulk density of the moon's highland crust is substantially lower than generally assumed. This low-bulk crustal density agrees well with data obtained during the final Apollo lunar missions in the early 1970s, indicating that local samples returned by astronauts are indicative of global processes."

""With our new crustal bulk density determination, we find that the average thickness of the moon's crust is between 21 and 27 miles (34 and 43 kilometres), which is about 6 to 12 miles (10 to 20 kilometres) thinner than previously thought," said Mark Wieczorek, GRAIL co-investigator at the Institut de Physique du Globe de Paris. "With this crustal thickness, the bulk composition of the moon is similar to that of Earth. This supports models where the moon is derived from Earth materials that were ejected during a giant impact event early in solar system history.""

"The map was created by the spacecraft transmitting radio signals to define precisely the distance between them as they orbit the moon in formation. As they fly over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly."

""We used gradients of the gravity field in order to highlight smaller and narrower structures than could be seen in previous datasets," said Jeff Andrews-Hanna, a GRAIL guest scientist with the Colorado School of Mines in Golden. "This data revealed a population of long, linear gravity anomalies, with lengths of hundreds of kilometres, crisscrossing the surface. These linear gravity anomalies indicate the presence of dikes, or long, thin, vertical bodies of solidified magma in the subsurface. The dikes are among the oldest features on the moon, and understanding them will tell us about its early history.""

Asteroids
At the time the radar images were taken, the asteroid was between 440,000 miles (710,000 kilometers) and about 430,000 miles (690,000 kilometers) distant. Asteroid 2015 TB145 safely flew past Earth on Oct. 31, at 10:00 a.m. PDT (1 p.m. EDT) at about 1.3 lunar distances (300,000 miles, 480,000 kilometers). To obtain the radar images, the scientists used the 230-foot (70-meter) DSS-14 antenna at Goldstone, California, to transmit high power microwaves toward the asteroid. The signal bounced of the asteroid, and their radar echoes were received by the National Radio Astronomy Observatory’s 100-meter (330-foot) Green Bank Telescope in West Virginia. The images achieve a spatial resolution of about 13 feet (4 meters) per pixel.

Jupiter
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 [Gigahertz] GHz to as low as 3 [Kilohertz] kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers.

"Details in radiation belts close to Jupiter are mapped from measurements that NASA's Cassini spacecraft made of radio emission from high-energy electrons moving at nearly the speed of light within the belts."

"The three views show the belts at different points in Jupiter's 10-hour rotation. A picture of Jupiter is superimposed to show the size of the belts relative to the planet. Cassini's radar instrument, operating in a listen-only mode, measured the strength of microwave radio emissions at a frequency of 13.8 gigahertz (13.8 billion cycles per second or 2.2 centimeter wavelength). The results indicate the region near Jupiter is one of the harshest radiation environments in the solar system."

"From Earth-based radio telescopes, the telltale radio emissions would be swamped out by heat-generated radio emissions from Jupiter's atmosphere, but Cassini was close enough to Jupiter in January 2001 to differentiate between the emissions from the radiation belts and those from the atmosphere."

"The belts appear to wobble as the planet turns because they are controlled by Jupiter's magnetic field, which is tilted in relation to the planet's poles."

Titan
"Due to advances in infrared/microwave astronomy and to the settlement of space missions to outer planets, recently the attention has shifted towards larger molecules, mostly of organic nature. Due to the tremendous complexity of its chemistry, the Titan’s ionosphere is the most pertinent example showing the importance of good chemical models for the interpretation of Cassini data. Heavy ions with masses over 100 amu have been detected in significant amounts into the Titan’s ionosphere below 1200 km [1]. Possible chemical structures include	PAHs, nitrile aromatic polymers [2], fullerenes [3] and polyphenyls [4] and such heavy particles have been proposed to act as seeds for aerosols formations [5]."

Uranus
Photometry over the course of half a Uranian year (beginning in the 1950s) has shown regular variation in the brightness in two spectral bands, with maxima occurring at the solstices and minima occurring at the equinoxes. A similar periodic variation, with maxima at the solstices, has been noted in microwave measurements of the deep troposphere begun in the 1960s. Stratospheric temperature measurements beginning in the 1970s also showed maximum values near the 1986 solstice. The majority of this variability is believed to occur owing to changes in the viewing geometry.

Detailed analysis of the visible and microwave data revealed that the periodical changes of brightness are not completely symmetrical around the solstices, which also indicates a change in the meridional albedo patterns. Finally in the 1990s, as Uranus moved away from its solstice, Hubble and ground based telescopes revealed that the south polar cap darkened noticeably (except the southern collar, which remained bright), while the northern hemisphere demonstrated increasing activity, such as cloud formations and stronger winds, bolstering expectations that it should brighten soon. This indeed happened in 2007 when the planet passed an equinox: a faint northern polar collar arose, while the southern collar became nearly invisible, although the zonal wind profile remained slightly asymmetric, with northern winds being somewhat slower than southern.

Interstellar medium
"The invention of microwave spectroscopy and the subsequent development of microwave astronomy has revealed two great régimes of interstellar chemistry: the dense molecular clouds and the circumstellar shells."

IK Tauri
"For both distributions, there is a dust shell of radius about 100 mas, or diameter of 200 mas, and two more or less discrete shells separated by about 240 mas. This approximately regular spacing is what produces a hump in the visibility curve in the (6-8.5) x 105 rad-1 range, though in somewhat different positions for the two years. It can be seen from Figure 4 that the prominent and well-defined outer dust shell expanded between 1992 and 1993. One should not expect that each dust shell emitted has exactly the same velocity, but if the motion of the outer shell is taken as 20.5 km s-1, an average of the 22 km s-1 velocity measured by CO line emission of material surrounding the star (Knapp & Morris 1985) and of 18.7 km s-1 for OH masers (Bowers et al. 1989), then the stellar distance can be obtained from the observed motion. The displacement of the outer shell is 17 mas between average dates of 1992 August 24 and 1993 September 14. From these values, the stellar distance is calculated to be 265 pc. This is in good agreement with the estimates of 270 and 220 pc by Knapp & Morris (1985) and Le Sidaner & Le Bertre (1996), respectively. Other estimates in the literature for the distance to IK Tau vary from 240 to 500 pc (Knapp & Morris 1985). If the velocity of the outer shell is indeed close to the average of OH and CO gas measured by microwave astronomy, the distance of 265 pc should be approximately correct and should confirm the distance estimates that have arrived at comparable values, rather than others that are substantially different."

MCG+01-38-005
"The [microwave] detection of interstellar formaldehyde provides important information about the chemical physics of our galaxy. We now know that polyatomic molecules containing at least two atoms other than hydrogen can form in the interstellar medium."

"Phenomena across the universe emit radiation spanning the entire electromagnetic spectrum — from high-energy gamma rays, which stream out from the most energetic events in the cosmos, to lower-energy microwaves and radio waves."

"Microwaves, the very same radiation that can heat up your dinner, are produced by a multitude of astrophysical sources, including strong emitters known as masers (microwave lasers), even stronger emitters with the somewhat villainous name of megamasers, and the centers of some galaxies. Especially intense and luminous galactic centers are known as active galactic nuclei. They are in turn thought to be driven by the presence of supermassive black holes, which drag surrounding material inwards and spit out bright jets and radiation as they do so."

"The two galaxies shown here, imaged by the Hubble Space Telescope, are named MCG+01-38-004 (the upper, red-tinted one) and MCG+01-38-005 (the lower, blue-tinted one). MCG+01-38-005 is a special kind of megamaser; the galaxy’s active galactic nucleus pumps out huge amounts of energy, which stimulates clouds of surrounding water. Water’s constituent atoms of hydrogen and oxygen are able to absorb some of this energy and re-emit it at specific wavelengths, one of which falls within the microwave regime. MCG+01-38-005 is thus known as a water megamaser!"

"Astronomers can use such objects to probe the fundamental properties of the universe. The microwave emissions from MCG+01-38-005 were used to calculate a refined value for the Hubble constant, a measure of how fast the universe is expanding. This constant is named after the astronomer whose observations were responsible for the discovery of the expanding universe and after whom the Hubble Space Telescope was named, Edwin Hubble."

RX J1347.5–1145
The NASA/ESA Hubble Space Telescope observed one of most massive known galaxy clusters, RX J1347.5–1145, seen in this Picture of the Week, as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). This observation of the cluster, 5 billion light-years from Earth, helped the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study the cosmic microwave background using the thermal Sunyaev-Zel’dovich effect. The observations made with ALMA are visible as the blue-purple hues.

Recent history
The recent history period dates from around 1,000 b2k to present.

"Penzias and Wilson discovered the remnant afterglow from the Big Bang and were awarded the Nobel Prize for their discovery. COBE first discovered the patterns in the afterglow. WMAP will bring the patterns into much better focus to unveil a wealth of information about the history and fate of the universe."

in the figure at the right, specifically the top left (TL) is the "Penzias and Wilson microwave receiver - 1965", (TR) a "Simulation of the sky viewed by Penzias and Wilson's microwave receiver - 1965" , (ML) "COBE Spacecraft, Painting - 1992" , (MR) "COBE's view of early universe- 1992" , (BL) "WMAP Spacecraft, Computer Rendering - 2001" , and (BR) "Simulated WMAP view of early universe".

Sciences
The submillimeter, millimeter, and microwave spectral line catalog is "a computer-accessible catalog of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10 000GHz (ie wavelengths longer than 30μm)."

Clocks
An atomic clock is a clock device that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS.

Low noise amplifiers
At right is an image of the QUIET module, a pseudo-correlation receiver comprising low noise amplifiers, phase shifters, detector diodes, and passive components. On the left is the first QUIET module which includes the "low noise amplifiers[, an] InP monolithic microwave integrated circuit (MMIC) high electron mobility transistor (HEMT) amplifiers." The upper right shows "an earlier prototype 90 GHz module. The modules are 1.25 x 1.14." The lower right is "the interior of a (2 x 2) 40 GHz module."

"Both Q and U are measured simultaneously by a single QUIET module with the introduction of an appropriate optical element: a circularly polarized orthomode transducer (OMT)."

At second right are schematic views "of a QUIET cryostat shown with a 91 element array of W-band modules."

"The horns are held at ≈ 20 K and shielded from 300K radiation by a radiation shield (shown only in the figure on the left) held at ≈ 80 K on the top and sides and the aluminum plate (also 80K) on the bottom."

The third right image is of the QUIET telescope. "The 2m design [...] accommodates 400 W-band receivers or 100 Q-band receivers, with each mirror machined as a single piece. [The] three 2m systems, [are] accommodated on the CBI platform as indicated in [the third right image]. The design uses two reflectors of approximately equal size in a crossed arrangement, and is known as a side fed Cassegrain (or crossed Dragone system). The primary mirror is parabolic and the secondary is a concave hyperboloid. By correctly selecting the angle between the two reflectors, a system that has a wide field of view with minimal cross-polarization results."

"The site [in the image on the left] for the QUIET telescopes [in the second left image with its dome down] is the Chajnantor scientific reserve in Chile, at an altitude of 5080 m. This site is recognized as one of the best in the world for millimeter and submillimeter astronomy. The site belongs to the state of Chile and is leased to the international Atacama Large Millimeter Array project (ALMA)."

Detectors
"The transmutation products are germanium acceptors (Ga), donors (As) and double donors (Se). It is evident that changing the relative isotopic composition directly affects the relative dopant concentrations. Growing germanium crystals consisting only of a mixture of 70Ge and 74Ge isotopes and using [Neutron Transmutation Doping] NTD allows the formation of a continuous series of crystals doped form purely p-type (70Ge 100%) to purely n-type (74Ge 100%) with all the possible compensation ratios between these two extremes. Our group has used NTD with natural Ge to form highly sensitive thermal detectors operating in the Kelvin and milliKelvin temperature range16) in a large number of far infrared and microwave astronomy and astrophysics experiments.17–19)"

Spacecraft
"The [Juno] spacecraft is built around a hexagonal cylinder bus measuring 3.5 m in diameter by 3.5 m high. Three solar panel wings extend from alternate sides of the hexagon giving a total diameter of approximately 20 m. A high gain antenna is mounted on top of the bus, with instruments mounted on the deck and propellant, oxygen, and pressurant tanks mounted within. At the center of the top deck is a 0.8 x 0.8 x 0.6 m titanium "vault" which houses the spacecraft avionics and critical systems to protect them from the severe jovian radiation environment. The vault has a mass of 150 kg and walls up to over a cm in thickness. Power is provided by ultra triple junction GaAs solar cells, covered with thick glass for radiation shielding, which are grouped into 11 solar panels, four on two of the wings and three on the other. (The end of the third wing is a boom structure holding science instruments.) The solar panels will produce a total of 18 kW at Earth and 400 W initially at Jupiter. The science payload comprises ten instruments: the Jovian Auroral Distributions Experiment (JADE), the Jupiter Energetic-particle Detector Instrument (JEDI), the Ultraviolet Spectrograph (UVS), the JunoCam, the Jovian Infrared Auroral Mapper (JIRAM), the Plasma Waves Instrument (Waves), the Microwave radiometer (MWR), the Fluxgate Magnetometer (FGM), the Advanced Stellar Compass (ASC), the Scalar Helium Magnetometer (SHM), and the Gravity Science experiment." Bold added.

Microwave telescopes
"The basic scientific goal of the Planck mission is to measure [cosmic microwave background] CMB anisotropies at all angular scales larger than 10 arcminutes over the entire sky with a precision of ~2 parts per million. The model payload consists of a 1.5 meter off-axis telescope with two focal plane arrays of detectors sharing the focal plane. Low frequencies will be covered by 56 tuned radio receivers sensitive to 30-100 GHz, while high frequencies will be covered by 56 bolometers sensitive to 100-850 GHz."

Wilkinson microwave anisotropy probe
"The Wilkinson Microwave Anisotropy Probe (WMAP) is a Medium-class Explorer (MIDEX) mission designed to elucidate cosmology by producing full-sky maps of the cosmic microwave background (CMB) anisotropy."

Explorer 66
The Cosmic Background Explorer (COBE) has aboard a differential microwave radiometer (DMR) labeled in the diagram at right.

The E and B experiment
The E and B Experiment (EBEX) will measure the cosmic microwave background radiation of a part of the sky during two sub-orbital (high altitude) balloon flights. It is an experiment to make large, high-fidelity images of the CMB polarization anisotropies. By using a telescope which flies at over 42,000 metres high, it is possible to reduce the atmospheric absorption of microwaves to a minimum. This allows massive cost reduction compared to a satellite probe, though only a small part of the sky can be scanned and for shorter duration than a typical satellite mission such as WMAP.

EBEX was launched on 29 December, 2012, near McMurdo Station in Antarctica.

"EBEX is meant to hone in on one specific feature of the CMB light that's been predicted, but never seen — a signature called B-type polarization, thought to have been produced by the gravity waves created by the universe's extremely rapid infant expansion, which happened even before the CMB light was released."

Explorer 49
Several satellites have served as observatories for radio waves and specifically for microwaves.

Explorer 49 [is] a 328 kilogram satellite launched on June 10, 1973 for longwave radio astronomy research. It had four 230-meter long X-shaped antenna elements, which made it one of the largest spacecraft ever built. Explorer 49 was placed into lunar orbit to provide radio astronomical measurements of the planets, the sun, and the galaxy over the frequency range of 25 kHz to 13.1 MHz.

Cosmic Anisotropy Telescope
The Cosmic Anisotropy Telescope (CAT), built in the mid 1990s, was the first interferometer to measure fluctuations in the cosmic microwave background (CMB). Its first results, published in 1996, were the highest resolution CMB detection at that time, and showed that the rise in fluctuation power towards scales of ~1 degree (l ~ 200) measured by the Saskatoon experiment were matched by a decline in power at smaller angles (l = 500-700), thus showing the existence of the long-predicted acoustic peak in the CMB power spectrum.

Relict-2
"A Russian microwave astronomy satellite called Relict-2 was the first one proposed to use a Sun-Earth L2 orbit in about 1990."

Orbital platforms
Skylab included an Apollo Telescope Mount, which was a multi-spectral solar observatory. Numerous scientific experiments were conducted aboard Skylab during its operational life, and crews were able to confirm the existence of coronal holes in the Sun. The Earth Resources Experiment Package (EREP), was used to view the Earth with sensors that recorded data in the visible, infrared, and microwave spectral regions.

Sun-synchronous orbital rocketry
A Sun-synchronous orbit (sometimes called a heliosynchronous orbit ) is a geocentric orbit which combines altitude and inclination in such a way that an object on that orbit ascends or descends over any given Earth latitude at the same local mean solar time. The surface illumination angle will be nearly the same every time. This consistent lighting is a useful characteristic for satellites that image the Earth's surface in visible or infrared wavelengths (e.g. weather and spy satellites) and for other remote sensing satellites (e.g. those carrying ocean and atmospheric remote sensing instruments that require sunlight). For example, a satellite in sun-synchronous orbit might ascend across the equator twelve times a day each time at approximately 15:00 mean local time. This is achieved by having the osculating orbital plane precess (rotate) approximately one degree each day with respect to the celestial sphere, eastward, to keep pace with the Earth's movement around the Sun.

The uniformity of Sun angle is achieved by tuning the inclination to the altitude of the orbit ... such that the extra mass near the equator causes the orbital plane of the spacecraft to precess with the desired rate: the plane of the orbit is not fixed in space relative to the distant stars, but rotates slowly about the Earth's axis. Typical sun-synchronous orbits are about 600–800 km in altitude, with periods in the 96–100 minute range, and inclinations of around 98° (i.e. slightly retrograde compared to the direction of Earth's rotation: 0° represents an equatorial orbit and 90° represents a polar orbit).

European remote sensing satellite (ERS) was the European Space Agency's first Earth-observing satellite. It was launched on July 17, 1991 into a Sun-synchronous polar orbit at a height of 782–785 km.

ERS-1 carried an array of earth-observation instruments that gathered information about the Earth (land, water, ice and atmosphere) using a variety of measurement principles. These included:
 * RA (Radar Altimeter) is a single frequency nadir-pointing radar altimeter operating in the Ku band.
 * ATSR-1 (Along-Track Scanning Radiometer) is a 4 channel infrared radiometer and microwave sounder for measuring temperatures at the sea-surface and the top of clouds.
 * SAR (synthetic aperture radar) operating in C band can detect changes in surface heights with sub-millimeter precision.
 * Wind Scatterometer used to calculate information on wind speed and direction.
 * MWR is a Microwave Radiometer used in measuring atmospheric water, as well as providing a correction for the atmospheric water for the altimeter.

To accurately determine its orbit, the satellite included a Laser Retroreflector. The Retroreflector was used for calibrating the Radar Altimeter to within 10 cm.

Its successor, ERS-2, was launched on April 21, 1995, on an Ariane 4, from ESA's Guiana Space Centre near Kourou, French Guiana. Largely identical to ERS-1, it added additional instruments and included improvements to existing instruments including:
 * GOME (Global Ozone Monitoring Experiment) is a nadir scanning ultraviolet and visible spectrometer.
 * ATSR-2 included 3 visible spectrum bands specialized for Chlorophyll and Vegetation

Aqua
"Aqua [...] is a NASA Earth Science satellite mission named for the large amount of information that the mission is collecting about the Earth's water cycle, including evaporation from the oceans, water vapor in the atmosphere, clouds, precipitation, soil moisture, sea ice, land ice, and snow cover on the land and ice. Additional variables also being measured by Aqua include radiative energy fluxes, aerosols, vegetation cover on the land, phytoplankton and dissolved organic matter in the oceans, and air, land, and water temperatures."

"It continues transmitting high-quality data from four of its six instruments, AIRS [Atmospheric Infrared Sounder], AMSU [Advanced Microwave Sounding Unit], CERES [Clouds and the Earth's Radiant Energy System], and MODIS [Moderate Resolution Imaging Spectroradiometer], and reduced quality data from a fifth instrument, AMSR-E [Advanced Microwave Scanning Radiometer-EOS]. The sixth Aqua instrument, HSB [Humidity Sounder for Brazil — VHF band], collected approximately nine months of high quality data but failed in February 2003."

"Aqua follows a kind of polar orbit known as a Sun-synchronous orbit, which means it crosses the equator at the same local time during each pass. Aqua’s orbit ascends from south to north during the daylight hours, crosses near the North Pole, circles around Earth’s nighttime side, and crosses near the South Pole to return to the daytime side."

Hypotheses

 * 1) Once literature searching has brought you to the state of the science, it is time to prepare an original research effort. Control groups and proof of concept are tools that can help to verify a model approach to an astronomical phenomenon.