Half-time for MASCOT – half the journey is completed
On December 3rd 2014, the French-German MASCOT asteroid lander was launched with its carrier probe Hayabusa2 from Tanegashima, an island about 40 kilometres south of the Japanese mainland. With MASCOT halfway to its destination, we look back on all that has happened since the launch.
At the beginning of 2015, MASCOT's spare flight unit, the so-called Flight Spare (FS), was refurbished and made ready. On Earth, this identical 'twin' of the asteroid lander serves as a reference system for the flight unit, the Flight Model (FM). The spare unit underwent the same qualification tests as the flight model and can also be used for advanced unit tests that were no longer possible for the FM due to scheduling constraints. These additional tests mainly focused on getting the best possible performance out of the system and on precisely calibrating the parameters required for the landing in October 2018. To achieve this, the scientific instruments on MASCOT performed a series of measurements.##markend##
Several were carried out with organic substrate mixtures and real meteorite samples in order to test the French infrared spectral microscope. The tests on the spare unit confirmed the ability of the MASCOT system to accomplish these tasks later with the parameters set independently on the asteroid and to process the data and prepare them for the delivery. The German magnetometer was tested once more in a magnetically neutral environment, in which all instruments were operated with a 'real' MASCOT flight battery (identical to the one on board the asteroid lander). With this calibration, it was possible to represent the characteristic curves of the largest sources of interference, which can be filtered out later from the measurements on the surface of the asteroid.
Test series were also conducted on the communication elements responsible for data transmission to determine the realistic connection parameters of the antenna, as well as its switch algorithm for high transmission rates at different distances and corresponding power modes. Very extensive tests were also carried out on MASCOT's primary test batteries. These specifically assessed the interaction between the standard power supply, the distribution unit, and the four scientific payloads, which are the main power consumers of the system. Only with the correct settings, a customised measuring sequence, and the proper initial thermal conditions will MASCOT be able to ensure that it can draw even the last reserves from its compact power supply.
The flight spare unit is the workhorse for the development team in Bremen. Similarly, the ground staff at the control centre in Cologne needs another independent MASCOT model. The so-called Ground Reference Model (GRM) is used for the testing and validation of communication and operation sequences before they can be transferred to the flight model in orbit. For this purpose, spare MASCOT parts and earlier testing and qualification models were refurbished and reused to create a cost-effective replica of the MASCOT system in a user-friendly table configuration. Upon completion, the ground reference model was transferred by Bremen engineers to Cologne on 3 February 2016. There was a briefing on how to handle the hardware as well as intensive training on programming the On-board Computer Software. This step is much like the delivery of a well-known smartphone along with developer software for creating your own program routines and Apps. With extensive development, testing and construction, it was demonstrated that MASCOT works. Now it is up to the colleagues in Cologne to learn how to control MASCOT. Of course, everyone involved is hoping that not too many bugs need to be fixed. A large-scale recall could be somewhat difficult. The two yearly communication checks with the MASCOT flight model in orbit have been completed so far without any complications, as was the control of the internal mechanisms.
All the signs so far point to a successful mission as it crosses its equator. However, we must not forget that unexpected problems can occur at any time in the merciless environment of space, especially during interplanetary missions. The entire MASCOT team is working meticulously to investigate all possibilities and include them in further planning. However, this mission is still a stab in the dark, a journey into the unknown. Or, to put it in famous, but slightly changed words:
"Space, the final frontier. Writing in the year 2016. These are the voyages of the starship Hayabusa2 which, with its strong MASCOT crew, is on a four and a half year mission to explore a new world, find signs of life and new answers for mankind. Many light-seconds from Earth, Hayabusa2 is boldly going where no man has gone before."
We are all keeping our fingers crossed!