Swarms of small satellites could communicate amongst themselves to collect data on important weather patterns at different times of the day or year, and from multiple angles. Such swarms, using machine learning algorithms, could revolutionize scientists’ understanding of weather and climate changes.
Engineer Sabrina Thompson is working on software to
enable small spacecraft, or SmallSats, to communicate with each other, identify
high-value observation targets, and coordinate attitude and timing to get different
views of the same target.
“We already know that Saharan dust blowing over to the
Amazon rainforests affects cloud formation over the Atlantic Ocean during
certain times of the year,” said Thompson, who works at NASA’s Goddard Space
Flight Center in Greenbelt, Maryland. “How do you capture that cloud formation?
How do you tell a swarm of satellites what region and time of day is the best
to observe that phenomenon?”
Under Thompson’s plan, scientists would establish a
set of requirements for observations and define high-value targets. Then the
software would take over, enabling a spacecraft swarm to figure out how to move
relative to one another to best observe these targets. Strategies might also
change based on time of day, season, or the region being observed. The
spacecraft also would use onboard machine learning to improve viewing
strategies over time.
Setting the following spacecraft to maximize drag and the leader to minimize drag will cause the follower to drop in altitude and catch up to the leader. Credits: NASA/Sabrina Thompson
“There are several types of swarm
configuration being considered,” Thompson said. “One might be a swarm where
satellites will be in different orbits, which will allow them to view a cloud
or other phenomenon at different angles. Another swarm could view the same
phenomena with similar view, but at different times of the day. A third type of
swarm might combine both, with some satellites in the same orbit, following one
another with some time offset, and other satellites which may be in orbits with
different altitudes and/or inclinations.”
While a swarm would stay within the same orbit,
individual spacecraft could even use something called differential drag control
— manipulating the forces caused by Earth’s atmosphere dragging against the
orbiting craft — to control the time separation between each spacecraft
relative to others in the swarm, she said. “The length of time it takes to
perform a differential drag maneuver depends on the spacecraft mass and area,
as well as the orbital altitude. For instance, it can take as long as one year
or as short as a couple of days, even hours.”
“With multiple spacecraft in one formation to view the
same target,” Thompson said, “you can see a cloud, for instance, not just from
the top, but from the sides as well.” In a different formation, you can see
that cloud at different stages of its life-cycle from multiple SmallSats
passing at different times.
A SmallSat like this
one, working with a swarm of similar spacecraft with more narrow-angle,
high-resolution polarimeters, could potentially revolutionize understanding of
weather formation and processes. Credits: NASA/SDL/Jose Vanderlei Martins
Working with University of Maryland – Baltimore County (UMBC) professor
Jose Vanderlei Martins, Thompson helped develop the Hyper-Angular Rainbow
Polarimeter (HARP) CubeSat that launched from the International
Space Station (ISS) just over a year ago. An updated version of its
instrumentation, called HARP2, will fly on the Plankton, Aerosol, Cloud, ocean
Ecosystem (PACE) mission planned for launch in 2023.
A swarm of SmallSats like HARP, sharing information and coordinating
coverage, could advance weather forecasting, disaster reporting, and climate
modeling in the long term, Vanderlei Martins said. To get there, scientists
need the combination of wide and narrow fields of view and high-resolution
imagery to better understand the dynamics of weather system development.
“Ideally, I like to have a satellite with a wide field of view observing
larger phenomenon,” he said. “However, a small satellite covering a large area
cannot make high spatial resolution observations. Nevertheless, you can use it
as a surveyor type of satellite to identify the area of interest. Then you have
others with a narrower field of view, getting higher resolution, getting much
more detail.”
Enabling the swarm to make decisions and share information is crucial.
Vanderlei Martins said, “These sorts of decisions need to be made in minutes.
You don’t have time for ground control to be involved.”
Thompson noted that reducing reliance on ground control and communications
networks also frees up resources for SmallSat missions with limited budgets.
As an aerospace engineer working towards an atmospheric physics degree at
the University of Maryland, Baltimore County, Thompson went back to school to
learn more about the Earth science requirements that drive her work as an
innovator. “I also really wanted to understand climate change.”
How aerosol particles and clouds interact is crucial to understanding
climate change. Polarimeters can provide a wealth of data about particles
suspended in the atmosphere -- from smoke, ash, and dust to water droplets and
ice, each species of particle polarizes light reflected from it in detectable
ways.
“At a basic level, my research involves evaluating the geometry between
instruments on the satellite and the sun,” Thompson said. “These instruments
are passive. They require a certain geometry relative to the ground target and
Sun to retrieve the science data we want.”
Her algorithms will determine the most suitable combinations of orbit and
instrument field of views to give the largest probability of observing a cloud
with the appropriate geometry to retrieve science data. Then it would plan and
execute maneuvering schemes for each spacecraft to achieve those geometries
relative to the other satellites in the swarm.
This work to understand the structure and development of clouds ties in
with the Atmosphere Observing
System, or AOS, (formerly the Aerosols and
Clouds, Convection and Precipitation study identified as a priority in the 2017
Earth Decadal Survey. Vanderlei Martins and Thompson believe their swarm
technology complements AOS's science objectives and could enhance upcoming NASA
Earth science missions.
Banner Image: Two satellites on similar orbits collect valuable
perspectives on the same part of the atmosphere. Credit:
NASA/Sabrina Thompson
By Karl B. Hille
NASA’s Goddard Space Flight Center in Greenbelt, Md.
No comments:
Post a Comment