Cubesat offers template for future astronomy missions

The first NASA-funded small satellite for exoplanet science is continuing to gather data well beyond its expected lifetime. The Colorado Ultraviolet Transit Experiment, known as CUTE, a six-unit cubesat equipped with a telescope to funnel data to a spectrograph, traveled to sun-synchronous low-Earth orbit in September 2021 as a secondary payload on the NASA- U.S. Geological Survey Landsat 9 Earth-observation mission. CUTE was designed to operate in space for at least eight months. Twenty-seven months later, the satellite’s onboard instruments still are observing the dramatic atmospheric loss of “hot jupiters,” gas giants orbiting very close to bright stars. “This atmospheric escape is incredibly fast,” said Kevin France, CUTE principal investigator at the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP), which assembled, tested and operates the satellite. “The materials are coming out so fast that they are dragging all the heavy elements out of the atmosphere with them.” Based on CUTE’s success, two additional NASA-funded, LASP-led missions have adopted similar mission and instrument designs. “CUTE’s been a great success, particularly given that we didn’t really know if we could do it for the amount of money that we proposed,” France told SpaceNews at the American Geophysical Union conference here. Lessons learned from CUTE are helping researchers “figure out how to build small spacecraft, how to build small instruments and how to have a student-led team,” France said.

The Colorado Ultraviolet Transit Experiment, known as CUTE, is a cubesat launched in 2021 to characterize the composition and mass-loss rates of exoplanet atmospheres. Credit: University of Colorado Laboratory for Atmospheric and Space Physics

Smallsat Astronomy

The budget for developing, assembling and operating CUTE through the summer of 2024 is about $5.5 million.

“At this cost, we’re still figuring out how to make things work,” France said. “So, working and doing science is batting above your average.”

The missions mimicking CUTE are 12-unit cubesats Sprite and Mantis.

Sprite, which stands for Supernova remnants Proxies for Reionization and Integrated Testbed Experiment, is scheduled for launch in 2024. The $4 million mission will study how gas and dust is processed in galaxies and how energetic ionizing radiation is transported from stars to the intergalactic medium between galaxies.

Mantis, short for Monitoring Activity from Nearby sTars with uv Imaging and Spectroscopy, is an $8.5 million campaign to observe how high-energy radiation from stars influences the habitability of planets.

Ingenuity and Chance

CUTE remains operational more than two years after launch thanks to ingenuity and luck.

The tiny satellite was sent into orbit at a higher altitude than mission planners expected. As a result, CUTE is expected to reenter Earth’s atmosphere in 2027, instead of late this year as originally scheduled.

Additional time in orbit means extra wear and tear on hardware.

“Every time we have a problem, we figure out a new way to operate the spacecraft,” France said.

When the satellite’s primary and backup memory storage cards failed, for example, mission operators learned to communicate directly with CUTE’s scientific payload.

“We send the data down directly from the science payload to the ground and we bypass the spacecraft altogether,” France said.

Distant Galaxies

Cubesats have been widely adopted for civil and commercial space missions since LASP researchers proposed CUTE in 2016.

At the time, “we were beginning to believe we could study the sun and Earth’s upper atmosphere with cubesats,” France said. “But the idea that we could be pointed at targets that are 300, 400 light years away and do high-precision astronomical measurements from the cubesat was ambitious.”

Now that CUTE has shown the potential, small satellites could play key roles in observing distant galaxies, black holes “and all the other things that we’re interested in studying,” France said.

NASA CubeSat Will Shine a Laser Light on the Moon's Darkest Craters

As astronauts explore the Moon during the Artemis program, they may need to make use of the resources that already exist on the lunar surface. Take water, for instance: Because it's a heavy and therefore expensive resource to launch from Earth, our future explorers might have to seek out ice to mine. Once excavated, it can be melted and purified for drinking and used for rocket fuel. But how much water is there on the Moon, and where might we find it? This is where NASA's Lunar Flashlight comes in. About the size of a briefcase, the small satellite - also known as a CubeSat - aims to detect naturally occurring surface ice believed to be at the bottom of craters on the Moon that have never seen sunlight. "Although we have a pretty good idea there's ice inside the coldest and darkest craters on the Moon, previous measurements have been a little bit ambiguous," said Barbara Cohen, principal investigator of the mission at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Scientifically, that's fine, but if we're planning on sending astronauts there to dig up the ice and drink it, we have to be sure it exists." Managed by NASA's Jet Propulsion Laboratory in Southern California, the spacecraft is a technology demonstration: It will seek to achieve several technological firsts, including being the first mission to look for water ice using lasers. It will also be the first planetary spacecraft to use a "green" propellant, a new kind of fuel that is safer to transport and store than the commonly used spacecraft propellant hydrazine.

"A technology demonstration mission like Lunar Flashlight, which is lower cost and fills a specific gap in our knowledge, can help us better prepare for an extended NASA presence on the Moon as well as test key technologies that may be used in future missions," said John Baker, Lunar Flashlight project manager at JPL.

Peering Into the Shadows

Over the course of two months, Lunar Flashlight will swoop low over the Moon's South Pole to shine its lasers into permanently shadowed regions and probe for surface ice. Found near the North and South Poles, these dark craters are thought to be "cold traps" that accumulate molecules of different ices, including water ice. The molecules may have come from comet and asteroid material impacting the lunar surface and from solar wind interactions with the lunar soil.

"The Sun moves around the crater horizon but never actually shines into the crater," said Cohen, whose team includes scientists at the University of California, Los Angeles, John Hopkins Applied Physics Laboratory and the University of Colorado. "Because these craters are so cold, these molecules never receive enough energy to escape, so they become trapped and accumulate over billions of years."

Lunar Flashlight's four-laser reflectometer will use near-infrared wavelengths that are readily absorbed by water to identify any accumulations of ice on the surface. Should the lasers hit bare rock as they shine into the South Pole's permanently shadowed regions, their light will reflect back to the spacecraft, signaling a lack of ice. But if the light is absorbed, it would mean these dark pockets do indeed contain ice. The greater the absorption, the more widespread ice may be at the surface.

While the CubeSat can provide information only about the presence of ice on the surface, and not below it, Lunar Flashlight seeks to fill a critical gap in our understanding of how much water ice these regions possess. "We will also be able to compare the Lunar Flashlight data with the great data that we already have from other Moon-orbiting missions to see if there are correlations in signatures of water ice, thereby giving us a global view of surface ice distribution," added Cohen.

The mission is detailed in a new paper published in the April 2020 issue of IEEE Aerospace and Electronic Systems Magazine.

Lunar Flashlight is funded by the Small Spacecraft Technology program within NASA's Space Technology Mission Directorate. The program is based at NASA's Ames Research Center in California's Silicon Valley. It will be one of 13 secondary payloads aboard the Artemis I mission, the first integrated flight test of NASA's Deep Space Exploration Systems, including the Orion spacecraft and Space Launch System (SLS) rocket launching from the newly upgraded Exploration Ground Systems at Kennedy Space Center in Florida.

Ending global plant tracking, Proba-V assigned new focus

ESA's cubic-metre-sized Proba-V minisatellite will soon end its nearly seven-year global mission to monitor the daily growth of all Earth's vegetation. As Copernicus Sentinel-3 takes on this task instead, Proba-V will be free to perform experimental monitoring over Europe and Africa - including co-observations with new companion missions. Despite its small size, Proba-V maintains a continent-spanning perspective: its main Vegetation imager has a 2250-km wide swath. This enables it to cover nearly the entire vegetated surface of the globe every day. Allowing for cloud cover, the mission builds up a complete snapshot of global plant growth every 10 days. Overall, the mission has acquired more than a petabyte of environmental data during its time in orbit. Proba-V's extremely wide view comes about because Vegetation is made up of three separate imaging telescopes, possessing 300 m spatial resolution, which rises to 100 m resolution in the central telescope - a marked improvement on the previous generation of Vegetation instruments. "Proba-V began as a 'gap-filler' mission to ensure data coverage between the Vegetation instruments flown on the full-sized Spot-4 and -5 satellites and Copernicus Sentinel-3," explains ESA Earth Observation operations manager Roberto Biasutti. "It started with a two-year mission lifetime, which was repeatedly extended, and the satellite remains in excellent overall health. So even though its global mission is due to end this June, shortly after its seventh birthday, the plan is to let it go on working."

Proba-V was launched into what is called a 'Sun-synchronous' orbit, where it keeps pace with the Sun as it circles Earth at 820 km altitude, allowing it the maximum possible observing daylight. This orbit is gradually decaying however, and the minisatellite lacks onboard thrusters to correct it. Tugged by the gravitational pull of Earth's equatorial bulge, its observing time is gradually growing earlier in the local morning.

"Basically one of the cameras on Proba-V will soon be observing night-time rather than daylight, meaning it cannot go on delivering daily global coverage anymore to continue the 20 year plus Vegetation time series, so its operational global mission has to end," comments Dennis Clarijs of VITO, the Belgian research and service centre processing and distributing Proba-V data to users.

"But this isn't the end of the mission. Instead ESA will be applying its excellent geometric and radiometric performance to make test observations in Europe and Africa, particularly the African Sahel where its results help provide early drought warnings.

"This means the more than 1800 research teams making use of Proba-V data today still have more data to look forward to, albeit on an experimental rather than operational basis. This is good because its 100-m imagery fills a particular niche, as a midway step between Copernicus Sentinel-2 and -3, able to resolve individual field delineations in some cases. Proba-V's 100-m imagery is also routinely used to cross-check other products, such as the Copernicus Global Land Service."

Proba-V will also be increasing its observations of the Moon. It is not generally known, but many Earth observation satellites routinely observe our planet's natural satellite along with Earth itself: the unchanging state of the lunar surface makes it an excellent calibration target.

In the past Proba-V made such lunar acquisitions on a monthly basis. Now the minisatellite will increase them, experimenting with changing frequencies and view angles for the benefit of future Earth-observing missions.

In addition, the plan is to launch in 2021 an additional tiny satellite carrying a single telescope version of the same Vegetation imager aboard Proba-V.

Roberto comments: "This companion mission is currently being developed by Belgian startup Aerospace Lab for launch next year. Based on a tiny 12-unit CubeSat - built up from standardised 10 cm cubic units - it will image the same targets as Proba-V areas at the same time except from a different viewing angle, allowing the creation of combined 'fusion' image products.

"A major motive behind the original Proba-V mission was to see if an instrument previously hosted on a full-sized satellite could do good work from a smaller platform. With this companion satellite we will raise the bar, using an even smaller, cheaper platform."

Another companion satellite is also being planned, to host either a thermal infrared imager or an hyperspectral instrument, both of which would offer valuable synergies with Vegetation observations, and test the feasibility of small satellite constellations entering operations in future.

Proba-V's orbital decay will finally bring it into complete darkness in October 2021, when it will either be shut down, or placed in suspended animation, awaiting a time when its orbit brings it into daylight again.

"There is a precedent for such an arrangement," adds Roberto, "with predecessor mission Proba-1, launched back in 2001, hosting a hyperspectral camera. Having passed through such a period of orbital darkness it is still observing to this day."

NanoRacks Completes 14th CubeSat Deployment Mission from International Space Station

NanoRacks successfully completed the 14th CubeSat Deployment mission from the Company's commercially developed platform on the International Space Station. Having released nine CubeSats into low-Earth orbit, this mission marks NanoRacks' 185th CubeSat released from the Space Station, and 217th small satellite deployed by NanoRacks overall. The CubeSats deployed were launched to the Space Station on the ninth contracted resupply mission for Orbital ATK (now Northrop Grumman Innovation Systems) from Wallops Island, Virginia in May 2018. NanoRacks offered an affordable launch opportunity, payload manifesting, full safety reviews with NASA, and managed on-orbit operations in order to provide an end-to-end solution that met all customer needs. "This mission yet again displays the continued reliability and uncontested consistency of NanoRacks' CubeSat deployment platforms, and what that performance enables," says NanoRacks Senior Mission Manager, Henry Martin. "Our customer base is the epitome of the diverse CubeSat market, and following the successful deployment of RemDeb only a couple weeks ago, this 14th airlock deployment mission shows the critical role NanoRacks continues to play in the growth of the commercial space industry."

NanoRacks is pleased to have to deployed seven satellites that were selected for flight by NASA's CubeSat Launch Initiative (CSLI) as part of the 23rd installment of the Educational Launch of Nanosatellites (ELaNa) mission, sponsored by the NASA Launch Services Program (LSP).

Additionally, NanoRacks is proud to have deployed the first satellites for two commercial startups.

Analytical Space's primary mission with their CubeSat, Radix, will be a demonstration of an optical data relay system. The satellite has the capability to receive transmissions at various frequency bands from the ground and/or from beta-test customer spacecraft already on orbit and store the data on board. Radix will then downlink the received data to the ground using laser communication.

EnduroSat One, the first Bulgarian amateur radio CubeSat mission, is a multipurpose CubeSat platform engineered for space application and research. The electrical power system and solar panels will provide power for the mission.

Two ultra-high frequency Transceivers type II and UHF deployable antenna will deliver a high-reliability communication system for tracking, telemetry and control (TT and C) and data. A network of actuators and sensors will enable spacecraft control and processing capabilities will be provided through the low power consumption and high performance onboard computer.

The CubeSats mounted externally to the Cygnus spacecraft from the May 2018 launch are scheduled to be deployed on Sunday, July 15th, pending nominal operations.

The satellites deployed were:

NASA ELaNa 23:

CubeRRT

EQUiSat

HaloSat

MemSat

RadSat-g

RainCube

TEMPEST-DCommercial CubeSats:

EnduroSat One (EnduroSat)

Radix (Analytical Space)

Small Packages to Test Big Space Technology Advances

This weekend, when the next cargo resupply mission to the International Space Station lifts off from NASA Wallops Flight Facility in Virginia, it will be carrying among its supplies and experiments three cereal box-sized satellites that will be used to test and demonstrate the next generation of Earth-observing technology. NASA has been increasing its use of CubeSats - small satellites based on several configurations of approximately 4 x 4 x 4-inch cubes - to put new technologies in orbit where they can be tested in the harsh environment of space before being used as part of larger satellite missions or constellations of spacecraft. The three CubeSat missions launching on Orbital ATK's ninth commercial resupply mission represent a broad range of cutting-edge technologies housed in very small packages. RainCube - a Radar in a CubeSat - is just that: a miniaturized precipitation-studying radar instrument that weighs just over 26 pounds. RainCube is smaller, has fewer components, and uses less power than traditional radar instruments. NASA's Earth Science Technology Office (ESTO) In-Space Validation of Earth Science Technologies (InVEST) program selected the project to demonstrate that such a diminutive radar can be operated successfully on a CubeSat platform.

This mission marks the first time an active radar instrument has been flown on a CubeSat.

If successful, RainCube could open the door for lower-cost, quick-turnaround constellation missions, in which multiple CubeSats work together to provide more frequent observations than a single satellite.

"A constellation of RainCube radars would be able to observe the internal structure of weather systems as they evolve according to processes that need to be better characterized in weather and climate forecasting models," said RainCube Principal Investigator Eva Peral of NASA's Jet Propulsion Laboratory in Pasadena, California.

RainCube will use wavelengths in the high-frequency Ka-band of the electromagnetic spectrum. Ka wavelengths work with smaller antennas (RainCube's deployable antenna measures at just half a yard, or meter, across) and allow an exponential increase in data transfer over long distances - making RainCube a demonstration in improved communications as well. JPL developed the RainCube instrument, while Tyvak Inc. developed the spacecraft.

CubeSats can also be used to test new subsystems and techniques for improving data collection from space. Radio frequency interference (RFI) is a growing problem for space-based microwave radiometers, instruments important for studying soil moisture, meteorology, climate and other Earth properties. As the number of RFI-causing devices - including cell phones, radios, and televisions - increases, it will be even more difficult for NASA's satellite microwave radiometers to collect high-quality data.

To address this issue, NASA's InVEST program funded a team led by Joel Johnson of The Ohio State University to develop CubeRRT, the CubeSat Radiometer Radio Frequency Interference Technology Validation mission.

"Our technology," said Johnson, "will make it so that our Earth-observing radiometers can still continue to operate in the presence of this interference."

RFI already affects data collected by Earth-observing satellites. To mitigate this problem, measurements are transmitted to the ground where they are then processed to remove any RFI-corrupted data.

It is a complicated process and requires more data to be transmitted to Earth. With future satellites encountering even more RFI, more data could be corrupted and missions might not be able to meet their science goals.

Johnson collaborated with technologists at JPL and Goddard Space Flight Center, Greenbelt, Maryland, to develop the CubeRRT satellite to demonstrate the ability to detect RFI and filter out RFI-corrupted data in real time aboard the spacecraft. The spacecraft was developed by Blue Canyon Technologies, Boulder, Colorado.

One of the radiometer-collected weather measurements important to researchers involves cloud processes, specifically storm development and the identification of the time when rain begins to fall.

Currently, weather satellites pass over storms just once every three hours, not frequently enough to identify many of the changes in dynamic storm systems. But the development of a new, extremely-compact radiometer system could change that.

NASA's Earth System Science Pathfinder program selected Steven Reising of Colorado State University and partners at JPL to develop, build, and demonstrate a five-frequency radiometer based on newly available low-noise amplifier technologies developed with support from ESTO.

The TEMPEST-D (Temporal Experiment for Storms and Tropical Systems Demonstration) mission will validate the miniaturized radiometer technology and demonstrate the spacecraft's ability to perform drag maneuvers to control TEMPEST-D's low-Earth altitude and its position in orbit. The instrument fits into a Blue Canyon Technologies 6U CubeSat - the same size CubeSat as RainCube and CubeRRT.

"With a train-like constellation of TEMPEST-like CubeSats, we'd be able to take time samples every five to 10 minutes to see how a storm develops," said Reising. This would improve upon the three-hour satellite revisit time, especially when collecting data on tropical storms like hurricanes that can quickly intensify and change.

RainCube, CubeRRT and TEMPEST-D are currently integrated aboard Orbital ATK's Cygnus spacecraft and are awaiting launch on an Antares rocket. After the CubeSats have arrived at the station, they will be deployed into low-Earth orbit and will begin their missions to test these new technologies useful for predicting weather, ensuring data quality, and helping researchers better understand storms.