When NASA’s most powerful rocket attempts its first flight this month, its highest-profile payload will be three instrumented mannequins, setting out on a 42-day journey to the moon and back. They are stand-ins for the astronauts who are supposed to take the 98-meter-tall rocket, called the Space Launch System (SLS), to the moon as soon as 2025, as part of NASA’s Artemis program. But there will be other passengers along for the ride when SLS departs on August 29: 10 CubeSats, satellites no bigger than a small briefcase, to probe the moon, asteroids, and the radiation environment of deep space.
The researchers who build those satellites have typical launch jitters: half of them may not have enough power to launch their missions. Stuck inside the rocket for more than a year due to launch delays, their batteries have dropped to a level where some may be unable to boot up and turn on their solar panels. “The longer we wait, the greater the risk,” says Morehead State University’s Ben Malphrus, principal investigator of the Lunar IceCube, one of the CubeSats with power concerns.
At stake is not just data, but tests of CubeSats as deep-space probes. “We’re in a transition phase from being a curiosity and training tool to being a real science platform,” says Malphrus. CubeSats are easy to assemble from standardized parts—from thrifty ion propulsion systems to pint-size radio transmitters—supplied by a growing commercial base. This allows researchers to focus on developing instruments capable of collecting new data – if they can condense them into a CubeSat package.
Small size and standardization also make CubeSats cheaper. At millions of dollars a pop, compared to hundreds of millions for a large, stand-alone satellite on its own rocket, they can take on risky missions, including hitchhiking aboard the unproven SLS. “When it comes to CubeSat, failure is an option,” Bhavya Lal, NASA’s associate administrator for technology, policy and strategy, said at a briefing earlier this month.
Many of the SLS cubesats will focus on the moon’s ice, which has intrigued researchers since NASA’s Lunar Prospector discovered signs of water in the late 1990s. Using a neutron detector, it peered into the cold, permanently shadowed regions in the polar craters. At most, the research discovered a curious suppression of neutrons – best explained by excess hydrogen in the uppermost meters of soil.
The researchers speculate that most of the hydrogen represents water ice from ancient impacts by comets or asteroids and is trapped in the coldest, darkest lunar recesses. But hydrogen can also be transplanted from the solar wind. When hydrogen ions in the air strike oxygen-bearing minerals in the lunar soil, it creates hydroxyl, which can be converted into water through subsequent reactions. If there is enough water on the moon, it can be used for agriculture and life support, and can be split into hydrogen and oxygen for rocket propellant. “It would be much more affordable than bringing it from Earth,” says Hannah Sargent, a planetary scientist at the University of Central Florida.
The Lunar Polar Hydrogen Mapper (LunaH Mapper), led by Craig Hardgrove of Arizona State University, Tempe, the SLS CubeSat, will attempt to improve on Lunar Prospector’s map with a daring orbit that will hover just 12 to 15 km above the South Pole. During 280 passes with its neutron detector, the team hopes to map excess hydrogen with a resolution of 20 to 30 kilometers, twice as fine as Lunar Prospector. “We can distinguish one [deep crater] from another,” says Hardgrove. Enrichment outside hydrogen-deficient craters, or cold hides, could indicate a relatively recent impact that erupted and redistributed the ice, he says.
The lunar icecube will carry a spectrometer that can detect infrared fingerprints of water or hydroxyl. Since this device relies on reflected light, it will be most sensitive to hydroxyl and water signals in sunlit regions at lower latitudes. “They’re really looking [effect of] The solar wind, day by day, says planetary scientist Benjamin Greenhagen of the Johns Hopkins University Applied Physics Laboratory.
When NASA launches its giant moon rocket, it will also carry 10 small satellites beyond low-Earth orbit. Some missions may have power problems at startup, with half of the satellites not allowed to recharge their batteries.
|NAME||purpose||Lead developer||Battery problems|
|Argomoon||CubeSats, monitor the release of rocket stages||Italian Space Agency|
|BioSentinel||Study the effects of radiation on yeast||NASA (Ames Research Center)|
|Cusp||Study the solar wind and magnetic fields||Southwest Research Institute||X|
|horseman||Image Earth’s plasmasphere||Japan’s space agency|
|LunaH map||Study lunar ice||Arizona State University||X|
|Moon Icecube||Study lunar ice||Morehead State University||X|
|LunIR||Testing a novel infrared spectrometer||Lockheed Martin||X|
|NEA Scout||Fly to an asteroid with a solar sail||NASA (Marshall Space Flight Center)|
|Omotenashi||Place a small lander on the surface of the moon||Japan’s space agency|
|Team Mile||Test the plasma thrusters||Miles Space Citizen Scientists||X|
Some cubesats have gone beyond the Moon. After SLS leaves Earth orbit and releases the probes, the Near-Earth Asteroid Scout (NEA Scout) will open a thin solar sail the size of a racquetball court. Powered by photons, it will navigate to 2020GE, a small asteroid between 5 and 15 meters across. About 2 years from now, it should come within 800 meters of the asteroid in a 3-hour flyby. Many large asteroids are loosely bound debris piles, but NEA Scout will test the expectation that 2020GE is dispersed too quickly for the faint pressure of sunlight to capture any debris, says Julie Castillo-Roguez, NEA Scout’s principal investigator for NASA’s Jet Propulsion Science. Laboratory.
Biosentinel, led by biologist Sergio Santa Maria of NASA’s Ames Research Center, will carry yeast strains in hundreds of microscopic wells, NASA’s first test of the biological effects of radiation beyond low-Earth orbit since the last Apollo mission in 1972. insecure Because of Earth’s magnetic field, organisms are more vulnerable to DNA damage caused by solar flares and galactic cosmic rays—a real concern for astronauts traveling to the Moon or Mars. From a sun-orbiting perch beyond the moon, optical sensors on BioSentinel will measure the health of yeast strains as they accumulate radiation damage by measuring cell growth and metabolism.
BioSentinel, NEA Scout, and three other CubeSats were allowed to recharge their batteries during the long wait at SLS. But five others were lucky, including both LunaH Map and Lunar IceCube. Some could not be recharged without being removed from the rocket. In other cases, NASA engineers feared that the process could cause a discharge that could damage the rest of the rocket. “We have to be very aware of the risk to the primary mission when we interface with these CubeSats,” says Jacob Bleicher, NASA’s chief exploration scientist.
Hardgrove says the LunaH map’s battery reserve is probably at 50% and the threat to the mission is high, as at 40% the CubeSat won’t be able to run through a set of initial operations and maneuvers before starting to recharge the solar panels. batteries. He says he pushed hard for an opportunity to recharge but was turned down by NASA officials. “You don’t agree to take stowaways and then kill them,” he says. Still, he realizes that cubesats are secondary payloads and is resigned to rolling the dice. “If you weren’t worried it wouldn’t be a CubeSat mission.”