After deploying EDM lander on Sunday, October 16, 2016, TGO was continuing its travel to reach Martian orbit after reducing speed and course change. In the meantime, EDM should land yesterday and send first data from Mars surface. Unfortunately, ESA still is not able to confirm successful landing of EDM.
Reaching Mars surface by EDM (Entry, Descent and Landing Demonstrator Module) and TGO (Trace Gas Orbiter) maneuver of injection into correct Mars orbit were key points of ExoMars 2016 mission. After seven months of space journey, TGO and EDM reached correct position for deployment procedure on October 16, 2016. Lander was deployed successfully, but landing was planned for October 19, along with orbit insertion of TGO. In spite of minor problems with receiving telemetry data from EDM after deployment, everything seemed to work fine, and ESA specialists in Darmstadt were waiting to confirm, that ESA and Roscosmos reached Mars with TGM and with EDM.
Landing was planned by ESA for 19th October, at 14:48 GMT. Weighing 600 kg and circular in shape lander (with diameter at 2.4 m and height of 1.65 m) was covered with shields of jettisoned thermal protection system and was equipped with parachute for reducing speed for over 1500 km/h. According to plan lander should deploy parachute, reduce speed, jettison thermal shield, leave conical shield with parachute, initialize three thrusters to stabilize flight and perform gentle touch down. This procedure was in fact experiment and results of landing are crucial for development of ExoMars 2020 lander designed and planned to be manufacture by NPO Lavochkin. EDM lander after landing should remain operational for at least 48 hours (it was only equipped with onboard batteries without solar arrays) and perform various experiments on Martian atmosphere. Landing zone was designated at Meridiani Planum (ellipse with 100 km of length and 15 km in the widest point). Since deploying on Sunday, EDM has been remaining in hibernation mode to save internal battery. At 14:25 GMT it switched to normal mode and probably at around 14:42 GMT it started to cross through dense layers of atmosphere. Delay of radio signal was around 10 minutes and first telemetry data should be received at 14:52 GMT with first signal from Mars surface around 15:01 GMT. Giant Metrewave Radio Telescope (GMRT) radio telescope in Pune, India, received signal from EDM. It confirmed only that lander has deployed parachute after entering Martian atmosphere at 14:42 GMT with speed of 21000 km/h. It deployed parachute on altitude of 11 km, just as it was planned. Still at that moment it was not confirmed if next phases of flight were conducted correctly. To remind: EDM Doppler radar should start to scan surface of landing zone from altitude of 7 km after it deployed heat shield from the bottom – lander should be released from upper heat shield with parachute and on altitude of 2 m conduct stabilizing burn and finally perform gentle touch down. It seems that last phases (releasing and reducing speed with hydrazine thrusters) were not conducted correctly. According to ESA (information was released today), EDM was ejected from upper part of heat shield system too early and probably on higher altitude than it was planned. Thrusters were initialized, but they worked not as long as it was planned (not to mention, that falling from higher altitude required prolonged time of working of thrusters):
“The data have been partially analyzed and confirm that the entry and descent stages occurred as expected, with events diverging from what was expected after the ejection of the back heat shield and parachute. This ejection itself appears to have occurred earlier than expected, but analysis is not yet complete.”
According to ESA, thrusters were ignited for at least 3 s to 4 s and telemetry data stopped to be transmitted 50 seconds before planned landing. According to ESA, problems probably appeared just in the moment of deploying parachute, but for final report on problems with EDM probably will have to wait little more.
Data transmitted by TGO and received today are after partial analyzing process, but are rather leaving no doubts, that there is any chance for establishing contact with EDM – we are just after first 24h of planned mission on Mars, which is limited by not rechargeable batteries to 48 hours.
TGO seems to have more luck comparing to EDM. After separation with EDM it has continued descent to Mars being on course to Meridiani Planum. On October 17 at 02:42 GMT, it performed raising burn to avoid collision using its 424 N thruster; most important burn during whole mission was conducted yesterday, at 13:14 GMT. It was done automatically by TGO, basing on command uploaded on October 18 (09:00 GMT). This burn put TGO into correct Mars orbit; it last longer than it was originally planned – instead 135 minutes, hydrazine thruster was working for 147 minutes. Trace Gas Orbiter reached highly elliptical orbit of 300 km x 96000 km with 4 sols (Martian days) period. TGO will spent there 8 sols and serve as data relay between EDM and Earth. After that, when onboard batteries of EDM will be discharged, it will begin lasting 7 months phase of aero-braking to change elliptical orbit for circular with altitude of 400 km and inclination at 74°. TGO will start its research on Mars atmosphere in second half of 2017, focusing mainly on searching for traces of methane, ethane and propane.
On picture above: ExoMars 2016 and ExoMars 2020 – different aspirations, same objective – Mars.