Philae lander on comet 67P/Churyumov-Gerasimenko (via ESA/Rosetta/Philae/CIVA)
The Philae lander's epic adventure this week left scientists and the public on edge as she bounced twice before landing in the shadow of a cliff on comet 67P/Churyumov-Gerasimenko. Considering this mission has been 10 years in the making due to the distance of the comet from Earth, scientists were hoping and praying that Philae would fly off into deep space or run out of power before being able to gather data.
Luckily for them, Philae isn't hurtling off into space in zero gravity and was finally able to relay 60 hours of data back to HQ. However, not everything has gone to plan and the data collection process was far less than ideal due to the fact that Philae landed a whole kilometer away from the original landing space.
Due to Rosetta, an orbiter that works with Philae to gather data, scientists now know where Philae is and the general condition of the equipment. Ideally, Rosseta and Philae were supposed to work together to collect a year's worth of data from their comet expedition. However, there is a major change in plans considering Philae is now in sleep mode due to lack of battery power. Rosseta is still continuing the mission alone and scientists hope Philae will wake up as the comet nears the sun, which will power Philae's solar panel powered battery pack. Before Philae powered down, the team was able to capture a schematic of the comet and it's core by passing radio waves through the comet, and back and forth to each other. This data has yet to be analyzed and revealed.
Now, we're looking at what went wrong with the design and engineering of Philae and where scientists can go from here. There were a lot of mishaps with Philae's equipment that led up to Philae snoozing on the side of a comet. All in all, this was the first attempt to land a probe on a comet, so while it wasn't a fully successful mission, all was not lost.
Map of Philae Lander's instruments. (via ESA/ATG medialab)
The main issue that paved the way for further complications with Philae's mission was the poor landing. Engineers and designers had worked hard to limit the possibility of Philae bouncing on landing, but these foresights were squashed when Philae's harpoons failed to fire.
Philae was supposed to launch two harpoons into the surface of the comet and hunker itself onto the surface of the comet securely, without bouncing. In addition to securing Philae in place, the harpoons also had sensors that were meant to gather data. Scientists were unable to gather thermal and acceleration data from the surface of the comet for this reason. Currently the DLR (the German space agency) team have had to settle with pictures taken during Philae's landing and pictures taken from Rosetta to get a clearer idea of the comet's surface. Philae was also able to gather samples, but little is known as to how far Philae got in analyzing the samples.
So, against the odds, Philae bounced once, then bounced again, before making a rough landing on in the shade of a cliff face with one foot out into space. Once Philae was on the surface, the harpoons couldn't be deployed due to the high likelihood of the probe being ejected into space due to low gravity.
After this, DLR knew it would be a matter of time before Philae ran out of power in the shade of the comet. Philae needs 6-8 hours of sunlight to fully charge per day, but the comet is currently only getting three hours of sunlight per day. Perhaps future probes should attempt to decrease their charge time dramatically to prevent an event like this.
DLR rushed to collect as much data as possible before Philae's battery ran out and used Rosetta to help them locate the lander. In the end, they captured 60 hours of data successful from Philae, but the quality and quantity is dubious due to the lander being unable to dig far enough into the surface of the comet. This was a result of the unexpected landing position, which eventually had Philae on it's side, and the ice hard surface of the comet in the shaded area.
For instance, the MUPUS instrument (see picture above) was meant to hammer 1.5 meters into the comet's surface to study surface properties. While the instrument worked as planned, it was unable to dig far enough into the comet's surface to get an ideal sample.
The MUPUS sensors did however give scientists data on the tough surface of the comet, which gave them a clue that the landing area was full of water ice.
Philae was also able to drill and gain samples for analysis. The COSAC analysis sensors were only able to collect a preliminary analysis in 'sniff' mode of the samples. The analysis indicated that organic compounds were found, but did not seem to indicate more as of yet.
So far, it seems like the DLR team is happy to analyze the data they were able to gather about the surface of the comet, a preliminary compound analysis, and a three-dimensional study of the comet's internal structure. More details will be revealed as they present themselves.
For now, Rosetta is busy continuing to collect data and hoping that Philae wakes up. The scientists are trying to use Philae's moving instruments to push it into a better position where it can collect samples once it wakes up.
It seems that the design of this probe was very efficient in having each component serve multiple purposes. However, this left little room for error and contingency as an initial mistake, like the harpoons not firing, turned into other errors in Philae's ability to collect samples.
Perhaps, NASA's ideas of 'Swarmies' will become a better way to design landers that are cheap and easily replaceable to ensure that one mistake doesn't turn into a failed mission. However, the Philae was the first lander to land on a comet and deserves recognition for being able to collect any data at all. Time will tell whether the lander will be able to wake up and move the mission forward in the coming year.
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