Artist’s impression visualizing the ExoMars 2016 Trace Gas Orbiter, with its thrusters firing, beginning its entry into Mars orbit on October 19, 2016. Image credit: ESA / ATG Medialab.
ExoMars 2016, managed by ESA and Roscosmos, comprises the Trace Gas Orbiter (TGO) and an Entry, descent, and landing Demonstrator Module (EDM), also known as Schiaparelli.
The 577 kg Schiaparelli lander will separate from TGO today, October 16, with 3.7 million miles (6 million km) still to travel before entering the Martian atmosphere for a descent to a region in Meridiani Planum three days later, on October 19. Its descent will take just under six minutes, using a heatshield, parachute, thrusters and a crushable structure for the landing. At the same time, the 3.7 ton mothership will enter orbit around the fourth planet from the Sun.
“They are now on a high-speed collision course with Mars, which is fine for the lander – it will stay on this path to make its controlled landing,” said Michel Denis at mission control in Darmstadt, Germany.
“However, to get the mothership into orbit, we must make a small but vital adjustment on October 17 to ensure it avoids the planet. And on October 19 it must fire its engine at a precise time for 139 minutes to brake into orbit. We get just a single chance.”
A statement confirming the outcome of the separation will be streamed live from the main control room of ESA’s Spacecraft Operations Centre starting today at 10:30 a.m. EDT (7:30 a.m. PDT, 2:30 p.m. GMT, 4:30 p.m. CET).
TGO will make a detailed inventory of Mars’ atmospheric gases, with particular interest in rare gases like methane, which implies that there is an active, current source.
The orbiter aims to measure methane’s geographical and seasonal dependence and help to determine whether it stems from a geological or biological source.
It will start its science mission at the end of 2017, following a year of complex aerobraking maneuvers to circularize its orbit. It will also act as a relay for ESA’s ExoMars 2020 rover.
Overview of Schiaparelli’s entry, descent and landing sequence on Mars, with approximate time, altitude and speed of key events indicated. Schiaparelli is scheduled to separate from the TGO today, three days before arriving at Mars. 12 hours after separation, the TGO will perform a course correction to avoid entering the atmosphere, and will continue into Mars orbit. Then, on October 19, Schiaparelli will enter the atmosphere at an altitude of about 75 miles (121 km) and a speed of nearly 13,050 mph (21,000 km/h). In the three to four minutes that follow, it will be slowed by the increasing atmospheric drag, with the front shield of the aeroshell bearing the brunt of the heating. 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 1,050 mph (1,700 km/h) Schiaparelli will be 7 miles (11 km) above the surface and a parachute will be deployed. The parachute will slow Schiaparelli to around 155 mph (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 the aeroshell that had kept it safe en route to Mars. The lander will then activate its three hydrazine thrusters to control its speed. Radar will continuously measure the height above the surface. At an altitude of around 6.5 feet (2 m), Schiaparelli will briefly hover before cutting its thrusters, leaving it to free fall. The touchdown speed will be a few feet per second, with the impact absorbed by a crushable structure similar to the crumple zone in a car, 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. Image credit: ESA / ATG Medialab.
Simulated sequence of the 15 images that the descent camera on the Schiaparelli module should take during its descent to the surface of Mars on October 19. The camera will start taking images about one minute after the front shield has been jettisoned. In the simulated images shown here, this corresponds to the first image being taken from an altitude of about 2 miles (3 km). The camera takes images every 1.5 seconds: the final image in this simulated sequence is at one mile (1.5 km), but depending on Schiaparelli’s actual descent speed on the day, the final image may be acquired closer to the surface. The views are generated from images taken by the CTX context camera on NASA’s Mars Reconnaissance Orbiter of the center of the landing ellipse, and represent the ground-projected field-of-view expected from Schiaparelli’s Descent Camera (DECA) at each altitude. The landing ellipse with the simulated DECA image footprints is shown at the bottom of this graphic. If Schiaparelli does not land exactly in the center of the ellipse then the actual view will be different. Image credit: ESA / ATG Medialab / NASA / JPL / MRO / Mars Odyssey.
Schiaparelli will test a range of technologies to enable a controlled descent and landing on Mars in preparation for future missions, including a heatshield, a parachute, a propulsion system and a crushable structure.
It also carries a small science package that will record the wind speed, humidity, pressure and temperature at its landing site, as well as obtain the first measurements of electric fields on the surface of Mars that may provide insight into how dust storms are triggered.
There is no scientific camera like those found on other landers or rovers — including the ExoMars rover that is planned for launch in 2020.
Schiaparelli does, however, carry a small technical camera, a refurbished spare flight model of the Visual Monitoring Camera flown on ESA’s Herschel/Planck spacecraft to image the separation of the two craft after their joint launch.
Its role is to capture 15 black and white images during the descent that will be used to help reconstruct the module’s trajectory and its motion, as well giving context information for the final touchdown site.
The camera will start taking images around a minute after Schiaparelli’s front shield is jettisoned, when the module is predicted to be about 2 miles (3 km) above the surface. This will result in images covering about 6.5 sq. miles (17 sq. km) on the surface.
The images will be taken at 1.5 s intervals, ending at an altitude of about one mile (1.5 km), covering an area of roughly 1.8 sq. miles (4.6 sq. km).
Then, at an altitude of about 0.7 miles (1.2 km), the parachute and rear cover will be jettisoned, and the thrusters ignited. The thrusters will cut out just 6.5 feet (2 m) above the surface, with the module’s crushable structure absorbing the force of impact.
Schiaparelli will target the center of a 62 x 9.3 mile (100 x 15 km) landing ellipse, in a relatively flat area in Meridiani Planum, close to the equator in the southern hemisphere.
The real images taken on October 19 will be stored in Schiaparelli’s memory before being beamed up to NASA’s Mars Reconnaissance Orbiter and downlinked to Earth on October 20.
