Skip to main content
U.S. flag

An official website of the United States government

USGS Hosting Constellation Mission Operations Working Group in Sioux Falls

It sounds like a kind of science-fiction fantasy—space trains chugging along on orbital tracks 705 kilometers above the Earth.

In fact, they are real—in a manner of speaking.

graphic of satellite constellation
Carefully coordinated constellation formations of satellites flying in close proximity at 705 kilometers above Earth, including Landsat 7, are able to provide collective information about the condition of the planet.(Public domain.)

Every morning, Landsat 7 and NASA’s Terra satellite barrel across the equator at roughly 10 a.m. Mean Local Time (MLT), flying in close formation to each other. Every afternoon around 1:30 p.m. MLT, six other satellites—starting with NASA’s Orbiting Carbon Observatory (OCO) 2, followed by Japan’s Global Change Observation Mission (GCOM), NASA’s Aqua mission, the joint NASA-French Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, NASA’s CloudSat mission, and NASA’s Aura mission—fly similarly in close proximity in what is called the Afternoon- or A-train.

While each satellite operates independently of the others, these carefully coordinated constellation formations enable something collectively greater. It’s called synergy, and it means that more information about the condition of the Earth is obtained from these combined observations than would be possible from the sum of observations taken independently.

This Tuesday through Thursday (June 12-14), representatives from the USGS, NASA, France’s Centre national d'études spatiales (CNES) (English: National Centre for Space Studies) agency, and the Japan Aerospace Exploration Agency (JAXA) office will gather in Sioux Falls, SD, for the Constellation Mission Operations Working Group (MOWG) meeting. It is the first time this semi-annual meeting has come to South Dakota. The MOWG’s primary focus is to discuss the status of each mission, including longevity estimates, on-orbit anomalies, instrument status, near-term and extended operation plans, and any decommissioning plans.

 “A great deal of conversation is based on physics and orbital mechanics, and basically being good neighbors in terms of informing each other on what our missions are doing,” said Jim Lacasse, Landsat Operations Project Manager at EROS.

There will be plenty of other interesting presentations at the MOWG conference as well. They’ll talk about conjunction event statistics that relate to when satellites pass dangerously close to objects in space. There will be an optional conjunction assessment, and a session on the progress and advances with covariance realism—or assessing the unknowns that come into play when trying to decide whether a satellite is potentially in harm’s way.

While collisions in space are rare, they have happened. In February 2009, a spent Russian COSMOS satellite slammed into an Iridium satellite, destroying both. It was the worst space debris event since China intentionally destroyed one of its aging weather satellites in 2007.

At the Sioux Falls meeting, the different mission representatives will talk about how they do Risk Management Maneuvers to avoid such collisions. “It’s kind of a sharing among experts in terms of what we do, because there’s still a bit of an art to maneuvering, and deciding when to maneuver,” Lacasse said. “The (MOWG) team gets together to share that information.”

In flying seconds to minutes apart on the same orbital track, the constellation of satellites is able to provide comprehensive information about key atmospheric components or processes, and thus a more complete answer to many questions than would be possible from any single satellite taken by itself. That information is helping scientists figure out:

  • What are the aerosol types in the atmosphere, and how do the constellation’s observations match global emission and transport models?
  • How do aerosols and cloud layering contribute to the Earth Radiation Budget? That budget is a concept used for understanding how much energy the Earth gets from the sun, and how much the Earth’s surface, atmosphere, oceans, and ice mass radiate back to outer space. If the Earth retains more energy from the sun, the Earth warms and emits more infrared energy. If the Earth emits more of this energy than it absorbs, the planet cools.
  • What is the vertical distribution of cloud water and ice in cloud systems? Information on producing vertical profiles of cloud water and ice content can lead to improved estimates of these parameters in weather and climate models.

“They each have their own objectives, such as imaging land, computing land temperature or identifying atmospheric components,” Lacasse said of the various satellites. “But they can be combined to generate better data products. That’s the reason for these trains, these constellations … for the science.”