LEO, MEO or GEO? Diversifying orbits is not a one-size-fits-all mission (Part 3 of 3)

  • Published
  • By Lisa Sodders, SSC Public Affairs
If you watch weather reports on the nightly news or any program on cable tv, you are most likely reaping the benefits of satellites in Geosynchronous Orbit, also known as GEO.

Satellites in GEO are 22,236 miles above the earth’s equator and move in sync with the Earth’s daily rotation, completing one revolution every 24 hours. Sensors in GEO provide a wider field of view compared to Low Earth and Medium Earth orbits. They also provide 24/7 coverage of a given region. That makes GEO ideal for weather monitoring systems, such as the National Oceanic and Atmospheric Administration’s GOES system.

“The magic of a GEO orbit is if you’re sitting on the ground…you know where that satellite is. It’s not streaking across the sky – it just sits right there,” says Gregory Henning, a project leader who specializes in space debris simulations with the Aerospace Corporation.

Satellite transmissions from GEO are also easier to capture from ground radars because the sensors are always in the same position relative to Earth.

“Television has used that orbit quite a bit – satellite TV will have a dish on the roof pointed at that one spot in the sky,” Henning notes.

GEO is also a powerful platform for national defense and surveillance capabilities. It currently hosts many of the SBIRS satellites that provide the nation’s “unblinking eye,” enabling 24/7 missile warning and tracking capabilities.

“If you can plant a satellite that can essentially stare (at one spot) and it doesn’t have to worry about flying over and gimballing its sensor or its camera to capture an image – it can capture an image of a region at any time of day from GEO any time it wants, as long as it’s sitting above that point on Earth,” Henning explains.

However, much like MEO orbits, it costs more to put a satellite into GEO. It also takes longer for a signal to make its way down from GEO, which can introduce lag times in applications such as satellite internet. The extremely high altitude also requires the use of very large, complex and expensive instruments to capture and deliver clear images.

“Satellites in GEO and HEO (High Earth Orbit) provide a wide field of view,” notes Col. Heather Bogstie, senior materiel leader for the Resilient Missile Warning, Tracking, and Defense Acquisition Delta at Space Systems Command. “But as the threat and ballistic missile technology has changed, particularly with regard to hypersonic missiles and hypersonic glide vehicles, the need to detect and track dim and fast moving targets drives us to a different architecture (and different orbits).”

To address these emerging threats, SSC is planning to deploy missile warning, tracking and defense sensors in LEO and MEO orbits to augment the existing constellation in GEO.

“This is the first mission area to receive a force design from the Space Warfighting and Analysis Center (SWAC),” Bogstie says. The design calls for placing Overhead Persistent Infrared (OPIR) sensors in various orbits, including LEO and MEO, to deliver a robust set of OPIR capabilities to deter and defeat the emerging threat.

Sensors in LEO and MEO are closer to the Earth, so they can capture more detailed views compared to sensors in GEO. The downside is that you need more of them to achieve the same field of view of the Earth that you get with a single satellite in GEO. But with enough assets, they can work as a family of sensors to achieve the same effect. And because satellites bound for LEO and MEO are generally smaller, they are more cost-efficient to build and less energy-intensive to launch.

“This (multi-orbit) design is based on improved sensor technology paired with an abundance of commercial space vehicles to give us affordable options to place more sensors closer to the targets we need to detect and track,” says Bogstie. “In addition, by placing our sensors in varied orbits we gain multiple views of the same area and targets — enhancing our geometry with additional look angles and range. Overall, we gain increased detection and tracking accuracy.”

Whether it’s in LEO, MEO or GEO, developing sensors to take advantage of diversified orbits is one important way that Space Systems Command is delivering resiliency in space.

Test Your Orbital Knowledge: Choose the answer that doesn’t fit.
1. A satellite in Geosynchronous Orbit:
A. Holds the same position over the earth
B. Is located 22,236 miles above the Earth’s Equator
C. Completes one revolution every 48 hours

2. Compared to other orbits, satellites in Geosynchronous Orbit are generally:
A. Bigger and fewer in number
B. More cost efficient to produce and launch
C. Have a wider field of view

3. Satellites in Geosynchronous Orbit:
A. Are used for weather monitoring
B. Are used for missile warning and tracking
C. Include 31 satellites that comprise the GPS constellation

1. C. Satellites in GEO complete one revolution every 24 hours
2. B. Satellites in GEO are more expensive to produce
3. C. The GPS constellation is located in Medium Earth orbit