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After months of simulations, flight controllers at European Space Operations Center, ESOC, in Darmstadt, Germany, conduct final phase of training in the runup to the ExoMars-2016 launch in March 2016. Click to enlarge. Credit: ESA

On June 13, 2016, CaSSIS camera onboard ExoMars took first picture of the Red Planet with a resolution of 460 kilometers per pixel. The Tharsis region of Mars, home to the planet's largest volcanoes, faces the spacecraft in this view. Credit: ESA

An artist rendering of the ExoMars-2016 spacecraft in cruise configuration during the flight between the Earth and Mars. Credit: ESA

The ExoMars-2016 team celebrates the success of the deep-space maneuver on July 28, 2016. Click to enlarge. Credit: ESA

ExoMars-2016 completes deep space maneuvers

On July 28, 2016, half way between Earth and Mars, the Trace Gas Orbiter, TGO, fired its 424-newton main engine for 52 minutes, changing the spacecraft's velocity by 326 meters per second and resulting in slightly lower speed for the ExoMars-2016 arrival at the Red Planet. Another smaller maneuver was conducted on August 11.

Previous chapter: ExoMars-2016 mission

Officially known as the deep-space maneuver, DSM, it was the longest engine burn for the ExoMars-2016 mission before the Mars orbit insertion on October 19, 2016. As a result of the July 28 orbit correction, the spacecraft will need less propellant during its maneuvers in the vicinity of the planet and the Schiaparelli lander will experience slightly less thermal loads during its planned entry into the Martian atmosphere.

In preparation for the deep-space maneuver, on July 13, the TGO flight team pressurized the propulsion system aboard the spacecraft with helium and on July 15, uploaded commands for a small, one meter per second test firing, which was originally scheduled on July 18, at 13:00 CEST. However ESA's mission control characterized the first attempt as "unsatisfactory," due to a "misconfiguration error." Fortunately, the second test-firing attempt on July 21 was fully successful, ESA said.

Before starting the deep-space maneuver, reaction wheels onboard the TGO were used to place the spacecraft into proper orientation for the engine firing and the probe's solar panels were locked into the so-called boost position to prevent damage to their delicate rotation mechanisms. The large high-gain antenna dish aboard the TGO was also stored, preventing its operation during the maneuver. Instead, mission control relied on a small low-gain antenna, which transmitted only carrier signal without telemetry data. Still, by measuring the Doppler shift of the carrier signal, flight controllers were able to monitor changing velocity of the spacecraft resulting from the engine thrust in near-real time with a few-minute delay needed for radio waves to reach the Earth.

According to ESA, the deep-space maneuver began at 09:30 GMT (11:30 CEST, 5:30 a.m. EDT). The maneuver was closely monitored by ESA’s mission control in Darmstadt, Germany, who followed the craft’s signals via the highly sensitive radio dish at New Norcia, Australia, ESA announced.

Flight dynamics engineers at the European Space Operations Center, ESOC, said that during the maneuver, the engine had underperformed by just 0.01 percent, characterizing its operation as "very, very accurate."

After the completion of the first deep-space maneuver, the second shorter engine firing was conducted as scheduled on August 11, 2016, at 11:30 CEST, at a distance of around 96 million kilometers from Earth. That maneuver lasted 155 seconds.

It was to follow by a pair of minor trajectory adjustments, known as the Trim Correction Maneuvers, TCMs, on September 19 and October 14, 2016, to further fine-tune the Mars-approach trajectory.

A second campaign of navigation measurements, known as "delta-DOR," was conducted in September or October. It should help to determine exact parameters for the Mars orbit injection to be performed by the TGO and the final descent trajectory for the Schiaparelli lander.

Next chapter: ExoMars-2016 arrives at Mars

Read (and see) much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:

Page author: Anatoly Zak; Last update: October 15, 2016

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