Schiaparelli did more things right than it did wrongby Svetoslav Alexandrov
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| It was easy for some people to point out that previous failure and say, “Look, the USA tried to land a craft on Mars in 1976 and succeeded right away without previous attempts, while Europe tried twice and both attempts ended in a failure.” |
In 2016, I published an article discussing why the Schiaparelli mission should be counted as an overall success (see “Why ESA’s Schiaparelli Mars can still be considered an overall success”, The Space Review, October 24, 2016). The report summary confirms my opinion. I still think that Schiaparelli was judged unfairly in the days after the mishap occurred, and that’s why I plead for reconsideration of Schiaparelli’s worth.
There are two factors in my opinion that contributed to the negativity in public perceptions of the mission. The first is that Schiaparelli was not Europe’s first attempt to land on Mars. The British Mars lander Beagle 2 flew to Mars with ESA’s Mars Express back in 2003, and it was never heard from again after detaching from the mothercraft. It was easy for some people to point out that previous failure and say, “Look, the USA tried to land a craft on Mars in 1976 and succeeded right away without previous attempts, while Europe tried twice and both attempts ended in a failure.”
Moreover, certain critics compared Schiaparelli’s overall performance to that of Beagle 2. While the fate of Beagle 2 couldn’t be confirmed right away after landing, the lander was found more than a decade later in photos taken by Mars Reconnaissance Orbiter (see “Found dog”, The Space Review, January 19, 2015). Apparently, Beagle 2 was sitting intact on the Mars surface and had even partially deployed its solar panels. Was Beagle 2 more successful than Schiaparelli, as those critics claimed? No, I don’t think so, and it’s quite inaccurate to compare a powered lander such as Schiaparelli to the airbag system employed by Beagle 2.
The second factor was a deep misunderstanding of what the goals of Schiaparelli were. People in general tend to assume that the orbiters are “boring” and the landers are “cool”. While the primary goal of the ExoMars program is to search the life on Mars, this wasn’t the task of Schiaparelli, but a job that will be done by the currently operated Trace Gas Orbiter and the rover which will be launched in 2020. I believe that the general public may have been misled to think that the goal cannot be reached just because Schiaparelli has crash-landed.
| Schiaparelli was primarily a test lander, and test flights are judged by different criteria compared to regular missions. |
While these factors seem convincing at first glance, the overall picture is somewhat different. Schiaparelli was not a “sexy” lander. It wasn’t supposed to dig into the surface of Mars to search for microorganisms, or conduct experiments to look for DNA or amino acids. It didn’t even have a surface camera to take photos of the surroundings. Schiaparelli was meant to be an entry, descent and landing demonstrator. It did carry some very simple scientific experiments. Some of them were expected to gather data from the surface but, due to the crash, never stood a chance to do so. However there were also some experiments carried out during the descent, and ESA once again reminded us in the press release about the investigation that these were successful and some scientific data about the Martian atmosphere was collected.
Schiaparelli was primarily a test lander, and test flights are judged by different criteria compared to regular missions. An engineering test is a good one depending on the number of steps executed and the data obtained. Coincidentally, just hours after the report of Schiaparelli was published, the private company Rocket Lab launched its first Electron rocket on a test flight. The rocket failed to reach orbit, but it did reach space and many of the test goals were fulfilled: first stage ignition, stage separation, second stage ignition, and payload fairing separation. The company announced that the test was an overall success and many space enthusiasts thought the same, too. The engineers have the data in their hands and they are happy.
So why isn’t Schiaparelli judged on the same ground? Schiaparelli was also able to execute most of the planned steps successfully. Here they are, according to the published report:
- Correct separation from the orbiter
- Correct wake-up from hibernation
- Correct detection of the Martian atmosphere
- Correct entry and aerobraking
- Correct detection of the parachute deployment time
- Correct jettison of the front shield
- Correct functioning of the Radar Doppler Altimeter.
There are only three steps that have not been demonstrated:
- Backshell and parachute svoidance maneuver (it was not necessary with the lateral velocity measured)
- Retro-powered descent phase down to drop point of two meters above the surface
- A free fall survival from the drop point.
And there are some steps which were demonstrated, but with wrong timing:
- Backshell and parachute separation, which occurred earlier than expected
- Successful switch to surface mode and initialization of instruments, which was demonstrated during freefall.
In contrast to Schiaparelli, Beagle 2 wasn’t presented as a test lander. It was supposed to be a fully-operational astrobiology mission, with a main focus “to establish whether there is convincing evidence for past life on Mars or to assess if the conditions were ever suitable.” Beagle 2 was meant to work for about 180 sols (Martian days) after landing, while Schiaparelli wasn’t expected to last more than eight sols. Beagle 2 was equipped with all of the necessary instruments to fulfill its scientific program, but none of those tasks were related to testing entry, descent, and landing (EDL) technologies. The EDL sequence was just supposed to work and that’s that.
| If there’s at least a slightly accurate comparison, it’s between Schiaparelli and the old Soviet mission Mars 6 from the Mars 73 program, which crash-landed on Mars in 1974. |
Moreover, Beagle 2 did not have a telemetry system during reentry, so even if there’s some evidence that the lander may have survived touchdown, there are still many questions that remain unanswered. Why did the solar panels fail to deploy as planned? Were the airbags insufficient to protect it from the impact? Did the parachute deploy on time? Were there any other problems before and after the parachute deployment? Since Beagle 2 was silent upon the descent, there’s no way we could know the answers to such questions.
Schiaparelli not only sent critical engineering data as well as scientific data from the Martian atmosphere during descent, it did it in a groundbreaking way: for a very first time a landing craft was communicating with a craft going in orbit around the Red Planet at the same time. This is an important achievement that cannot be understated.
If there’s at least a slightly accurate comparison, it’s between Schiaparelli and the old Soviet mission Mars 6 from the Mars 73 program, which crash-landed on Mars in 1974. This lander was able to transmit some data during descent to its mother craft, although the mothership was just flying by and not entering orbit as it was the case with ExoMars Trace Gas Orbiter. Unfortunately, much of the data obtained from Mars 6 turned out to be unreadable due to transistor flaws, which plagued the whole Mars 73 program. This mission is considered to have been a partial success.
Schiaparelli is already partially successful from an engineering point of view and, in my opinion, it has a chance to be more scientifically successful than Mars 6. Earlier this year, during the Sixth International Workshop on the Mars Atmosphere, an article was presented by Ferri et al. with the title “Atmospheric Mars Entry and Landing Investigations & Analysis (AMELIA) by ExoMars 2016 Schiaparelli Entry Descent Module”. It stated that the radio signal and the telemetry data set, which is essential from the achievement of the AMELIA scientific objectives, are “under analysis to investigate the reasons for the Schiaparelli’s landing failure and are under embargo.” Now, with the investigation now complete, the embargo should be lifted. Schiaparelli may have things to say about the structure of the Martian atmosphere, and I can’t wait to see the results published in academic journals.