October 15, 2016 – The ExoMars program is a joint endeavor between the European Space Agency (ESA) and the Russian Federal Space Agency (Roscosmos). The first mission of the ExoMars program is ExoMars 2016, which consists of a Trace Gas Orbiter (TGO) and an entry, descent and landing demonstrator module known as Schiaparelli.
The main objective of the TGO is to search for evidence of methane and other trace atmospheric gases that could be signatures of active biological or geological processes. Schiaparelli’s main task is to demonstrate technologies needed to safely land on Mars, which will be needed for Europe’s 2020 rover mission. Schiaparelli also carries a small suite of scientific instruments.
The pair have almost completed their 496 million km journey, and are scheduled to separate on October 16, 2016, at 8:42 a.m. MDT, three days before reaching Mars. NASA’s 70-meter antennas in Canberra, Australia and Madrid, Spain will be listening and will be able to confirm the separation by measuring the changing Doppler shift of a carrier signal from the mission.
Twelve hours after separation, the TGO will perform a trajectory correction maneuver to avoid entering the Martian atmosphere. The two-minute engine firing will allow it to enter its orbit on October 19, when it will fire its engine for an additional 139 minutes to brake into Mars orbit.
Schiaparelli will be on a direct collision course with the Red Planet and for most of its three-day autonomous flight, the lander will be in hibernation mode to conserve its battery.
On October 19, Schiaparelli will enter the atmosphere at an altitude of about 121 km and a speed of nearly 21,000 km/h. In less than six minutes, it will use a heatshield, a parachute and thrusters to slow its descent before touching down on in the Meridiani Planum region close to the equator, absorbing the final contact with a crushable structure.
First, the lander will be slowed by the increasing atmospheric drag, with the front shield of the aeroshell bearing the brunt of the heat. This will slowly melt and vaporize, allowing the absorbed heat to be carried away from the rest of the spacecraft.
Once the speed has decreased to around 1700 km/h, at an altitude of about 11 km, a parachute is deployed. The parachute canopy unfurls in less than a second, and 40 seconds later, allowing for oscillation to die down, the front shield of the aeroshell will be jettisoned. The parachute will slow Schiaparelli to around 250 km/h, and then the back half of the aeroshell, with the parachute attached to it, will also be jettisoned. It will be drawn rapidly away from Schiaparelli, which will now be completely free of its protective aeroshell.
Schiaparelli will then activate its three hydrazine thrusters to control its speed. Radar will continuously measure the height above the surface starting at about 7 km. At around 2 meters, Schiaparelli will briefly hover before cutting its thrusters, leaving it to free fall to the surface. The touchdown speed will be a few meters per second, with the impact absorbed by a crushable structure on the underside of the lander, preventing damage to the rest of the module.
The entire entry, descent and landing sequence will be complete in less than six minutes.
Once safely on the surface, a small meteorological station (DREAMS) will operate for a few days. DREAMS will measure local weather conditions at the landing site, such as temperature, humidity, pressure, dust opacity, wind speed, and wind direction. It will also obtain the first measurements of electric fields on the surface of Mars that, combined with measurements of the concentration of atmospheric dust, will provide new insights into the role of electric forces in dust lifting, the trigger for dust storms. The science activities are designed to make the most of the limited energy available from the batteries, so they will be performed in set windows, rather than continuously, for approximately six hours per day.
The Trace Gas Orbiter, while firing its engine to break into orbit, will also record Schiaparelli’s descent and landing. The orbiter will detect and record critical events, such as Schiaparelli’s entry into the atmosphere, parachute deployment, heatshield release, touchdown and the start of surface activities. The data will be downloaded and reconstructed at a later time.
In the days following the descent, ESA’s Mars Express and NASA’s three orbiters will each serve as data relays, overflying Schiaparelli’s landing site once or twice per day, picking up signals from the lander, and relaying them to Earth. The module’s transmitter will switch on during a series of fixed slots to send recorded data to the orbiters overhead. These relay slots include 32 by NASA craft: 18 by the Mars Reconnaissance Orbiter (MRO), eight by Odyssey and six by MAVEN. ESA’s Mars Express will make 14 overflights.
The commands that will govern the Schiaparelli lander’s descent and touchdown on Mars were uploaded to the spacecraft last week. Schiaparelli’s time-tagged stored commands will ensure that the lander conducts its mission even when it’s out of contact with the Mars orbiters. Automated operation also ensures that the lander will revive from its power-saving sleep periods on the surface in time for communication links.
ExoMars is a cooperative project between ESA and Roscosmos. It comprises two missions: the Trace Gas Orbiter and the Schiaparelli entry, descent and landing demonstrator module, which were launched on March 14, 2016, and the ExoMars rover and surface platform, scheduled for launch in 2020.
Live coverage of ExoMars TGO arrival and Schiaparelli landing on Mars will begin on October 16 at 8:30 a.m. MDT. Watch all livestreaming events via ESA’s Livestream channel.