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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
How can I see the northern lights?
To see the northern lights, you need to be in the right place at the right time.
Auroras are the result of charged particles and magnetism from the Sun called space weather dancing with the Earth’s magnetic field. And they happen far above the clouds. So you need clear skies, good space weather at your latitude and the higher, more polar you can be, the better. You need a lot of patience and some luck is always helpful.
A smartphone can also really help confirm whether you saw a little bit of kind of dim aurora, because cameras are more sensitive than our eyes.
The best months to see aurorae, statistically, are March and September. The best times to be looking are around midnight, but sometimes when the Sun is super active, it can happen any time from sunset to sunrise.
You can also increase your chances by learning more about space weather data and a great place to do that is at the NOAA Space Weather Prediction Center.
You can also check out my project, Aurorasaurus.org, where we have free alerts that are based on your location and we offer information about how to interpret the data. And you can also report and tell us if you were able to see aurora or not and that helps others.
One last tip is finding a safe, dark sky viewing location with a great view of the northern horizon that’s near you.
[END VIDEO TRANSCRIPT]
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Last Updated Mar 26, 2025 Related Terms
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By NASA
5 min read
Atomic Layer Processing Coating Techniques Enable Missions to See Further into the Ultraviolet
Astrophysics observations at ultraviolet (UV) wavelengths often probe the most dynamic aspects of the universe. However, the high energy of ultraviolet photons means that their interaction with the materials that make up an observing instrument are less efficient, resulting in low overall throughput. New approaches in the development of thin film coatings are addressing this shortcoming by engineering the coatings of instrument structures at the atomic scale.
Researchers at the NASA Jet Propulsion Laboratory (JPL) are employing atomic layer deposition (ALD) and atomic layer etching (ALE) to enable new coating technologies for instruments measuring ultraviolet light. Conventional optical coatings largely rely on physical vapor deposition (PVD) methods like evaporation, where the coating layer is formed by vaporizing the source material and then condensing it onto the intended substrate. In contrast, ALD and ALE rely on a cyclic series of self-limiting chemical reactions that result in the deposition (or removal) of material one atomic layer at a time. This self-limiting characteristic results in a coating or etchings that are conformal over arbitrary shapes with precisely controlled layer thickness determined by the number of ALD or ALE cycles performed.
The ALD and ALE techniques are common in the semiconductor industry where they are used to fabricate high-performance transistors. Their use as an optical coating method is less common, particularly at ultraviolet wavelengths where the choice of optical coating material is largely restricted to metal fluorides instead of more common metal oxides, due to the larger optical band energy of fluoride materials, which minimizes absorption losses in the coatings. Using an approach based on co-reaction with hydrogen fluoride, the team at JPL has developed a variety of fluoride-based ALD and ALE processes.
(left) The Supernova remnants and Proxies for ReIonization Testbed Experiment (SPRITE) CubeSat primary mirror inside the ALD coating facility at JPL, the mirror is 18 cm on the long and is the largest optic coated in this chamber to-date. (right) Flight optic coating inside JPL ALD chamber for Pioneers Aspera Mission. Like SPRITE, the Aspera coating combines a lithium fluoride process developed at NASA GSFC with thin ALD encapsulation of magnesium fluoride at JPL. Image Credit: NASA-JPL In addition to these metal-fluoride materials, layers of aluminum are often used to construct structures like reflective mirrors and bandpass filters for instruments operating in the UV. Although aluminum has high intrinsic UV reflectance, it also readily forms a surface oxide that strongly absorbs UV light. The role of the metal fluoride coating is then to protect the aluminum surface from oxidation while maintaining enough transparency to create a mirror with high reflectance.
The use of ALD in this context has initially been pursued in the development of telescope optics for two SmallSat astrophysics missions that will operate in the UV: the Supernova remnants and Proxies for ReIonization Testbed Experiment (SPRITE) CubeSat mission led by Brian Fleming at the University of Colorado Boulder, and the Aspera mission led by Carlos Vargas at the University of Arizona. The mirrors for SPRITE and Aspera have reflective coatings that utilize aluminum protected by lithium fluoride using a novel PVD processes developed at NASA Goddard Space Flight Center, and an additional very thin top coating of magnesium fluoride deposited via ALD.
Team member John Hennessy prepares to load a sample wafer in the ALD coating chamber at JPL. Image Credit: NASA JPL The use of lithium fluoride enables SPRITE and Aspera to “see” further into the UV than other missions like NASA’s Hubble Space Telescope, which uses only magnesium fluoride to protect its aluminum mirror surfaces. However, a drawback of lithium fluoride is its sensitivity to moisture, which in some cases can cause the performance of these mirror coatings to degrade on the ground prior to launch. To circumvent this issue, very thin layers (~1.5 nanometers) of magnesium fluoride were deposited by ALD on top of the lithium fluoride on the SPRITE and Aspera mirrors. The magnesium fluoride layers are thin enough to not strongly impact the performance of the mirror at the shortest wavelengths, but thick enough to enhance the stability against humidity during ground phases of the missions. Similar approaches are being considered for the mirror coatings of the future NASA flagship Habitable Worlds Observatory (HWO).
Multilayer structures of aluminum and metal fluorides can also function as bandpass filters (filters that allow only signals within a selected range of wavelengths to pass through to be recorded) in the UV. Here, ALD is an attractive option due to the inherent repeatability and precise thickness control of the process. There is currently no suitable ALD process to deposit aluminum, and so additional work by the JPL team has explored the development of a custom vacuum coating chamber that combines the PVD aluminum and ALD fluoride processes described above. This system has been used to develop UV bandpass filters that can be deposited directly onto imaging sensors like silicon (Si) CCDs. These coatings can enable such sensors to operate with high UV efficiency, but low sensitivity to longer wavelength visible photons that would otherwise add background noise to the UV observations.
Structures composed of multilayer aluminum and metal fluoride coatings have recently been delivered as part of a UV camera to the Star-Planet Activity Research CubeSat (SPARCS) mission led by Evgenya Shkolnik at Arizona State University. The JPL-developed camera incorporates a delta-doped Si CCD with the ALD/PVD filter coating on the far ultraviolet channel, yielding a sensor with high efficiency in a band centered near 160 nm with low response to out-of-band light.
A prototype of a back-illuminated CCD incorporating a multi-layer metal-dielectric bandpass filter coating deposited by a combination of thermal evaporation and ALD. This coating combined with JPL back surface passivation approaches enable the Si CCD to operate with high UV efficiency while rejecting longer wavelength light. Image credit: NASA JPL Next, the JPL team that developed these coating processes plans to focus on implementing a similar bandpass filter on an array of larger-format Si Complementary Metal-Oxide-Semiconductor (CMOS) sensors for the recently selected NASA Medium-Class Explorer (MIDEX) UltraViolet EXplorer (UVEX) mission led by Fiona Harrison at the California Institute of Technology, which is targeted to launch in the early 2030s.
For additional details, see the entry for this project on NASA TechPort
Project Lead: Dr. John Hennessy, Jet Propulsion Laboratory (JPL)
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Last Updated Mar 18, 2025 Related Terms
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By NASA
NASA’s Jet Propulsion Laboratory used radar data taken by ESA’s Sentinel-1A satellite before and after the 2015 eruption of the Calbuco volcano in Chile to create this inter-ferogram showing land deformation. The color bands west of the volcano indicate land sinking. NISAR will produce similar images.ESA/NASA/JPL-Caltech A SAR image — like ones NISAR will produce — shows land cover on Mount Okmok on Alaska’s Umnak Island . Created with data taken in August 2011 by NASA’s UAVSAR instrument, it is an example of polarimetry, which measures return waves’ orientation relative to that of transmitted signals.NASA/JPL-Caltech Data from NASA’s Magellan spacecraft, which launched in 1989, was used to create this image of Crater Isabella, a 108-mile-wide (175-kilometer-wide) impact crater on Venus’ surface. NISAR will use the same basic SAR principles to measure properties and characteristics of Earth’s solid surfaces.NASA/JPL-Caltech Set to launch within a few months, NISAR will use a technique called synthetic aperture radar to produce incredibly detailed maps of surface change on our planet.
When NASA and the Indian Space Research Organization’s (ISRO) new Earth satellite NISAR (NASA-ISRO Synthetic Aperture Radar) launches in coming months, it will capture images of Earth’s surface so detailed they will show how much small plots of land and ice are moving, down to fractions of an inch. Imaging nearly all of Earth’s solid surfaces twice every 12 days, it will see the flex of Earth’s crust before and after natural disasters such as earthquakes; it will monitor the motion of glaciers and ice sheets; and it will track ecosystem changes, including forest growth and deforestation.
The mission’s extraordinary capabilities come from the technique noted in its name: synthetic aperture radar, or SAR. Pioneered by NASA for use in space, SAR combines multiple measurements, taken as a radar flies overhead, to sharpen the scene below. It works like conventional radar, which uses microwaves to detect distant surfaces and objects, but steps up the data processing to reveal properties and characteristics at high resolution.
To get such detail without SAR, radar satellites would need antennas too enormous to launch, much less operate. At 39 feet (12 meters) wide when deployed, NISAR’s radar antenna reflector is as wide as a city bus is long. Yet it would have to be 12 miles (19 kilometers) in diameter for the mission’s L-band instrument, using traditional radar techniques, to image pixels of Earth down to 30 feet (10 meters) across.
Synthetic aperture radar “allows us to refine things very accurately,” said Charles Elachi, who led NASA spaceborne SAR missions before serving as director of NASA’s Jet Propulsion Laboratory in Southern California from 2001 to 2016. “The NISAR mission will open a whole new realm to learn about our planet as a dynamic system.”
Data from NASA’s Magellan spacecraft, which launched in 1989, was used to create this image of Crater Isabella, a 108-mile-wide (175-kilometer-wide) impact crater on Venus’ surface. NISAR will use the same basic SAR principles to measure properties and characteristics of Earth’s solid surfaces.NASA/JPL-Caltech How SAR Works
Elachi arrived at JPL in 1971 after graduating from Caltech, joining a group of engineers developing a radar to study Venus’ surface. Then, as now, radar’s allure was simple: It could collect measurements day and night and see through clouds. The team’s work led to the Magellan mission to Venus in 1989 and several NASA space shuttle radar missions.
An orbiting radar operates on the same principles as one tracking planes at an airport. The spaceborne antenna emits microwave pulses toward Earth. When the pulses hit something — a volcanic cone, for example — they scatter. The antenna receives those signals that echo back to the instrument, which measures their strength, change in frequency, how long they took to return, and if they bounced off of multiple surfaces, such as buildings.
This information can help detect the presence of an object or surface, its distance away, and its speed, but the resolution is too low to generate a clear picture. First conceived at Goodyear Aircraft Corp. in 1952, SAR addresses that issue.
“It’s a technique to create high-resolution images from a low-resolution system,” said Paul Rosen, NISAR’s project scientist at JPL.
As the radar travels, its antenna continuously transmits microwaves and receives echoes from the surface. Because the instrument is moving relative to Earth, there are slight changes in frequency in the return signals. Called the Doppler shift, it’s the same effect that causes a siren’s pitch to rise as a fire engine approaches then fall as it departs.
Computer processing of those signals is like a camera lens redirecting and focusing light to produce a sharp photograph. With SAR, the spacecraft’s path forms the “lens,” and the processing adjusts for the Doppler shifts, allowing the echoes to be aggregated into a single, focused image.
Using SAR
One type of SAR-based visualization is an interferogram, a composite of two images taken at separate times that reveals the differences by measuring the change in the delay of echoes. Though they may look like modern art to the untrained eye, the multicolor concentric bands of interferograms show how far land surfaces have moved: The closer the bands, the greater the motion. Seismologists use these visualizations to measure land deformation from earthquakes.
Another type of SAR analysis, called polarimetry, measures the vertical or horizontal orientation of return waves relative to that of transmitted signals. Waves bouncing off linear structures like buildings tend to return in the same orientation, while those bouncing off irregular features, like tree canopies, return in another orientation. By mapping the differences and the strength of the return signals, researchers can identify an area’s land cover, which is useful for studying deforestation and flooding.
Such analyses are examples of ways NISAR will help researchers better understand processes that affect billions of lives.
“This mission packs in a wide range of science toward a common goal of studying our changing planet and the impacts of natural hazards,” said Deepak Putrevu, co-lead of the ISRO science team at the Space Applications Centre in Ahmedabad, India.
Learn more about NISAR at:
https://nisar.jpl.nasa.gov
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Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
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Last Updated Jan 21, 2025 Related Terms
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By NASA
NASA Administrator Bill Nelson, left, and Deputy Administrator Pam Melroy, right, present Bob Cabana, who served as a NASA associate administrator, astronaut, and a colonel in the United States Marine Corps, the President’s Award for Distinguished Federal Civilian Service, recognizing his exceptional achievements and public service to the nation, Jan. 10, 2025, at the Mary W. Jackson NASA Headquarters in Washington. The award, signed by President Biden, is the highest honor the federal government can grant to a federal civilian employee.Credit: NASA/Bill Ingalls Robert Cabana, who served as a NASA associate administrator, astronaut, and a colonel in the United States Marine Corps, received the President’s Award for Distinguished Federal Civilian Service, recognizing his exceptional achievements and public service to the nation. The award, signed by President Biden, is the highest honor the federal government can grant to a federal civilian employee.
NASA Administrator Bill Nelson and Deputy Administrator Pam Melroy presented Cabana with the award during a ceremony at NASA Headquarters in Washington on Jan. 10. Cabana most recently served as NASA’s associate administrator, which is the agency’s highest ranking civil servant, from 2021 until he retired from the agency at the end of 2023.
“A true public servant, Bob has spent his entire career in service to his country. I can think of no one more deserving of this rare honor than Bob,” said Nelson. “From his time as a naval aviator to his role as associate administrator of NASA, Bob has dedicated his life to improving his country. I join with President Biden in thanking Bob for his dedication and commitment.”
The award recognized Cabana for his roles as a Marine aviator, test pilot, astronaut and becoming the first American to enter the International Space Station. He was further recognized for continuing to push for the bounds of the possible, launching the James Webb Space Telescope, the Artemis I mission and the Orion spacecraft which will send humans back to the Moon for the first time in decades.
As a NASA astronaut, Cabana flew in space four times, including twice as commander. His final space shuttle flight in 1998 was the first International Space Station assembly mission. Cabana also was the director of the agency’s Kennedy Space Center in Florida for more than a decade. There he led its transition from retirement of the space shuttle to a multi-user spaceport once again launching NASA astronauts to low Earth orbit, and for the first time, doing so with commercial partners.
As NASA associate administrator, Cabana led the agency’s 10 center directors, as well as the mission directorate associate administrators at NASA Headquarters. He was the agency’s chief operating officer for more than 18,000 employees and oversaw an annual budget of more than $25 billion.
Cabana was selected as an astronaut candidate in June 1985 and completed training in July 1986. He logged 38 days in space during four shuttle missions. Cabana was a pilot aboard space shuttle Discovery on both the STS-41 mission in October 1990 that deployed the Ulysses spacecraft and the STS-53 mission in December 1992. He was the mission commander aboard space shuttle Columbia for the STS-65 mission in July 1994 that conducted experiments as part of the second International Microgravity Laboratory mission. He commanded space shuttle Endeavour for the STS-88 mission in December 1998.
Cabana was appointed a member of the Federal Senior Executive Service in 2000 and served in numerous senior management positions at NASA’s Johnson Space Center in Houston, ultimately becoming deputy director. He was named director of NASA’s Stennis Space Center in Mississippi in October 2007 and a year later was selected as NASA Kennedy director.
Born in Minneapolis, Cabana graduated from the U.S. Naval Academy in 1971 with a bachelor’s degree in mathematics. He became a naval aviator and graduated with distinction from the U.S. Naval Test Pilot School in 1981. In his career, Cabana logged over 7,000 hours in more than 50 different kinds of aircraft. He retired as a colonel from the U.S. Marine Corps in September 2000.
In addition to receiving the President’s Award for Distinguished Federal Service, Cabana’s accomplishments have been recognized with induction into the Astronaut Hall of Fame and being named an Associate Fellow in the American Institute of Aeronautics and Astronautics and a Fellow in the Society of Experimental Test Pilots. He has received numerous personal awards and decorations, including the Distinguished Flying Cross and the Presidential Distinguished Rank Award. He also is a recipient of the Rotary National Award for Space Achievement’s National Space Trophy.
For Cabana’s full bio, visit:
https://go.nasa.gov/3u9hGB2
-end-
Meira Bernstein / Jennifer Dooren
Headquarters, Washington
202-615-1747 / 202-358-1600
meira.b.bernstein@nasa.gov / jennifer.m.dooren@nasa.gov
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Last Updated Jan 13, 2025 EditorJessica TaveauLocationNASA Headquarters Related Terms
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