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A tightly choreographed dance between NASA’s Deep Space Network and Mars orbiters will keep the agency’s Perseverance in touch with Earth during landing and beyond.
When NASA’s Mars 2020 Perseverance rover touches down with the Ingenuity Mars Helicopter on the Red Planet on Feb. 18, they won’t be alone. From orbit, two robotic buddies will be playing a special role in the event by checking in on the mission’s vital signs from the moment Perseverance enters the atmosphere to long after it makes its first tracks on the Martian surface.
NASA’s Mars Reconnaissance Orbiter (MRO) and the Mars Atmospheric and Volatile EvolutioN (MAVEN) orbiter are a part of the Mars Relay Network, a constellation of spacecraft that serves as a lifeline to the current surface missions on Mars – NASA’s Curiosity rover and InSight lander.
While some commands and telemetry can be sent directly to and from Earth, for the most part, the huge quantities of science data collected by rovers and landers cannot, because it would take too long. Most data traveling back to Earth must first be sent to the Mars orbiters overhead, which then transmit the data tens of millions of miles through interplanetary space to radio antennas on Earth, including the antennas of NASA’s venerable Deep Space Network (DSN).
“It is a huge endeavor to maintain communications with our spacecraft throughout the solar system, but Mars surface missions take this commitment to another level,” said Bradford Arnold, DSN project manager at NASA’s Jet Propulsion Laboratory in Southern California. “Since Mars Global Surveyor (MGS) arrived in orbit in 1997, a steady stream of orbiters has been added, carrying relay radios and antennas, which provide highly efficient communications between surface landers and Earth. While the choreography of this relay scheme is now somewhat commonplace for assets in place, it is still extremely challenging to coordinate all the communication links for the very brief time during a lander’s arrival.”
This dance will ensure that the world can watch Perseverance’s entry, descent, and landing – a harrowing sequence of events that will begin as the rover’s interplanetary cruise ends.
Over the Horizon
As Perseverance enters the Martian atmosphere inside its protective aeroshell, the rover will switch between several of its onboard antennas to stay in contact with Earth. Some of these antennas use powerful X-band transmissions that can send small amounts of data directly to the DSN. Others use ultra high frequencies (or UHF) to communicate with MRO and MAVEN.
Managed by JPL for NASA’s Space Communications and Navigation program (SCaN), the DSN consists of several parabolic radio antennas at ground stations in Southern California, near Madrid, Spain, and outside Canberra, Australia. This configuration allows mission controllers to communicate with spacecraft throughout the solar system at all times throughout Earth’s daily rotation. During Perseverance’s landing, Madrid’s antennas will be trained on Mars, taking the lead when receiving data. The Goldstone complex near Barstow, California, will also be listening in as a backup.
Since the landing of NASA’s Mars Exploration Rovers Spirit and Opportunity in 2004, science data has been routinely relayed via the Mars orbiters to the DSN, beginning with MGS and then NASA’s veteran Odyssey orbiter, which has been circling Mars since 2001.
Because the final two minutes of Perseverance’s descent and landing will be mostly beyond Mars’ horizon from Earth’s perspective, “direct-to-Earth” X-band communications will be impossible, and the rover will communicate with Earth solely via MRO and MAVEN when it lands.
In orbit since 2006, MRO was designed as a science mission and to act as a communications relay for landed surface missions. But it received an upgrade to prepare for Perseverance’s landing.
“In the past year, the software of the MRO spacecraft and its UHF radio have been updated to allow the near-immediate return of data collected during EDL. MRO will capture the telemetry transmitted by Perseverance and use its 3-meter [10-foot] dish to transmit it immediately to Earth,” said Roy Gladden, manager of the Mars Relay Network at JPL. “We call this a ‘bent pipe’, which allows us to get word from Perseverance even though Mars is blocking our view from Earth.”