Are small satellites the solution for space weather monitoring?
With key space weather satellites expected to fail before U.S. and European agencies launch replacements, “small satellites may be the only way of averting a bleak future,” said Daniel Baker, director of the University of Colorado’s Laboratory for Atmospheric and Space Physics.
Many of the instruments the U.S. relies on to monitor solar flares, coronal mass ejections and other phenomena that pose a threat to satellites in orbit and technology on the ground are well beyond their anticipated life spans. The National Oceanic and Atmospheric Administration (NOAA) is sending new instruments into orbit on its latest generation of geostationary weather satellites but other updates to the space weather constellation are likely to fly years after current instruments fail. That’s prompting government, industry and academic experts to consider how cubesats and small satellites could help.
“Most of the measurements we’re making for operational space weather certainly can be done with smaller satellites,” said Douglas Biesecker, NOAA National Space Weather Prediction Center’s research and customer requirements section lead. “For certain problems, you want a bunch of distributed satellites.”
To date, large government satellites have been packed with multiple state-of-the-art sensors to provide exquisite detail of the space weather environment at a single point in space. While cubesats are not likely to replace the large observatories at the Earth-Sun L1 Lagrange point anytime soon, a constellation of the miniature spacecraft orbiting Earth at all longitudes and various altitudes would be helpful in monitoring energetic particles and magnetic fields, said Biesecker, a solar physicist and program scientist for NOAA’s Deep Space Climate Observatory, a 570-kilogram satellite launched in 2015 to track solar wind from L1, a gravitationally stable perch 1.5 million kilometers from Earth.
An aging observing network
Key space weather instruments only have a few years left. NASA’s Advanced Composition Explorer, sent to L1 in 1997 to monitor solar wind and energetic particles, is expected to run out of the propellant it needs to maintain its position around 2024. The Deep Space Climate Observatory has performed many of the same jobs at L1 since 2015 but it doesn’t have ACE’s ability to measure energetic particles.
One of NASA’s two Solar Terrestrial Relations Observatory or STEREO satellites, sent in 2006 to orbit the sun and provide imagery of coronal mass ejections and other phenomena, still works but by 2022 it will be too close to Earth to act as an L5 proxy, meaning it will no longer offer the unique vantage point to detect solar activity days before it reaches Earth.
The European Space Agency plans to continue operating the Solar and Heliophysics Observatory (SOHO) until sometime in the first half of the 2020s, when the spacecraft’s solar panels are expected to reach the point where they no longer provide necessary power. SOHO has monitored the sun’s coronal mass ejections from L1 since 1995.
To make up for those shortfalls, NOAA launched Geostationary Operational Environment Satellite-16 in 2016 and GOES-17 in 2018 with four space weather instruments. The next satellite in the series, GOES-T, is equipped with the same sensors and was slated to launch in 2020 before NASA discovered problems with the Advanced Baseline Imager’s cooling system. NOAA is seeking funding to install a fifth instrument, a Naval Research Laboratory compact coronagraph, on GOES-U set to launch in 2024.
In addition, NASA began soliciting information in October on future space weather satellites, instruments and services in anticipation NOAA’s proposed Space Weather Follow-On, an observatory at L1 to gather imagery of coronal mass ejection and monitor solar wind.
Meanwhile, Ball Aerospace is installing an energetic charged particle sensor on Weather System Follow-on-Microwave, an Air Force satellite to track ocean surface winds and tropical cyclone intensity. Starting in the early 2020s, the Air Force plans to install energetic charged particle sensors on all spacecraft.
Filling in holes
The new programs promise valuable data but space weather monitoring is an enormous job. It requires ongoing observation of the sun, its magnetic field and solar wind as well as Earth’s magnetosphere, ionosphere and thermosphere.
“The space weather environment is vast, reaching from the surface of the sun almost to the surface of the Earth,” said Dave Klumpar, director of Montana State University’s Space Science and Engineering Laboratory. “It is a large, highly complex, dynamic and nonlinear system.”
The new programs are not likely “to fill the holes in our observing platform; to look at sun in three-dimensions and understand its interactions with nearEarth space,” Baker said.
In 2012, Baker and NASA associate administrator Thomas Zurbuchen cochaired the National Research Council’s decadal survey on solar and space physics. That committee recommended annual expenditures of $100 million to $200 million, or $1 billion to $2 billion over a decade, for an operational space weather system.
“The agencies and Congress have not had the stomach for doing that,” Baker said. “We have a better chance of getting some pieces of this with small satellites rather than with large satellites.”
To Klumpar, who has focused on space weather since he worked in the University of Iowa laboratory of James Van Allen, the physicist who discovered Earth’s radiation belts, cubesats are an obvious solution.
“Constellations of dozens, hundreds, maybe even more, could provide the information needed to monitor space weather and ultimately predict how it will unfold,” Klumpar said. “The real enabler is the ability to put multiple platforms in disparate locations throughout the space environment to understand how that flow of interactions is proceeding.”
Students working under Klumpar and Harlan Spence, director of the University of New Hampshire’s Center for the Study of Earth, Oceans and Space, built pairs of two-kilogram Firebird cubesats sent into high inclination orbits in 2013 and 2015 to measure energetic bursts of electrons in Earth’s upper atmosphere.
The first pair gathered data for seven months. The second pair of Firebirds continues to gather data after more than four years. “We are very proud of that accomplishment and kind of amazed, too,” Spence said.
Firebirds and other space weather cubesats funded by the NASA and the National Science Foundation including the Colorado Student Space Weather Experiment from the University of Colorado, Boulder, Electron Losses and Fields Investigation from the University of California, Los Angeles, and Compact Radiation Belt Explorer from the Goddard Space Flight Center and Southwest Research Institute “are steppingstones to swarm and constellation missions,” Spence said. “Instead of focusing on single point measurements we are developing maps that are important not just for basic science but for space weather.”
Finding the right tool
Cubesats can’t perform all space weather monitoring jobs. The key is to match the satellite to the mission.
“In the last century, the tools we had available defined the job we did in space,” Larry Paxton, chief heliophysics scientist at the Johns Hopkins Applied Physics Laboratory, said by email. “Now, we have a range of capabilities enabled by relatively inexpensive, reliable and capable launch vehicles. Each class of satellite — and one must not forget the power of hosted payloads — enables us to provide cost-effective solutions for a particular need.”
A medium to large spacecraft would be needed, for example, to reach solar polar orbit to monitor the sun’s magnetic field, said Nicole Duncan, Ball Aerospace heliophysics advanced systems manager.
Satellites destined for L1 also will require extensive propellant plus a meter-sized antenna to transmit data 1.5 million kilometers to Earth, Larry Paxton, Johns Hopkins Applied Physics Laboratory’s chief scientist for heliophysics, said by email.
For other space weather missions, satellites could be built for Evolved Expendable Launch Vehicle Secondary Payload Adapters, said Makenzie Lystrup, Ball Aerospace Civil Space vice president. “You can create a constellation with that size without the expense of miniaturizing instrumentation, which you might have to do for the cubesat form factor,” Lystrup said.
Around Earth, though, nanosatellites or microsatellites could “enable better predictions of the space environment … precisely because we can afford more of them,” Paxton said. “More is definitely better when trying to characterize the spatial and temporal variability experienced in Earth’s geospace environment.”
Paxton cautioned against thinking of new space weather constellations as homogeneous or static.
“For science and monitoring missions, constellations of different classes of satellites, hosting different instruments and providing different services, may be the best solution to a critical challenge,” Paxton said. “Heterogeneous constellations enable us to adapt to evolving user needs and scientific questions; a satellite constellation should be viewed as infrastructure that, like any tool, can be updated as needs evolve.”
This article originally appeared in the Feb. 25, 2019 issue of SpaceNews magazine.