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Philae’s “little brother” going to an asteroid: MASCOT involvement


Philae’s “little brother” going to an asteroid: MASCOT involvement
​“15 years ago it would not have been possible to build MASCOT”
 
- Federico Cordero, Project Manager MASCOT On-Board Computer
 

When we meet Federico in an afternoon he doesn’t have much time for lunch. Time pressure is a significant factor that the Telespazio VEGA project team members have been faced with in the MASCOT mission. MASCOT, short for Mobile Asteroid Surface Scout, is a DLR payload that will be launched on-board the Japanese Hayabusa2 (HY2) spacecraft (JAXA) on from Tanegashima Space Centre and will be controlled from DLR’s MASCOT control centre in Cologne. The launch, initially planned for 30 November 2014, had to be re-scheduled due to bad weather conditis and took place on 3 December 2014.

Three years ago, also Telespazio VEGA became involved in MASCOT. Through its experience in previous interplanetary missions such as Rosetta as well as on-board software, the company was selected to support the German Aerospace Agency (DLR) in a variety of mission phases. 

While Philae was travelling technology moved on

On 12 November 2014, lander Philae of the ESA mission Rosetta has landed on a comet and Telespazio VEGA has also been heavily involved. However, although MASCOT can be considered Philae’s “little” brother, the two are not at all the same. Federico explains: “Philae was designed almost 15 years ago and launched 10 years ago. With MASCOT however, we started much later. In fact, take the on-board computer specifications for MASCOT: They are so strict that we could not have managed to build a similar unit 15 years ago. We did learn a lot from Philae, but technology moved so fast ever since that we had to start almost from scratch and complete it on a tight three year schedule.”

A light computer for the asteroid mission

In fact, Telespazio VEGA colleagues are nowadays spread across various company and client sites and mission phases. The team around Federico, based in Darmstadt at the Telespazio VEGA main office and at the European Space Operations Centre (ESOC), was responsible for one of the core elements of MASCOT: The central On-Board Computer (OBC).

MASCOT needs to be very light and small, so that it can fit on Hayabusa2. In addition, its power consumption is to be kept to a minimum so that the mission goals can be fulfilled by the small primary batteries.  At the same time, the hardware has to be reliable, tolerant to any single failure and performant, to ensure quick data processing of science data. The first task we were faced with was to translate the stringent system requirements into feasible specifications for the computer hardware inside the lander. For example its mass, dimensions, interfaces, redundancy, processing capacity and how robust it needs to be to any environmental influences during launch, the trip to the asteroid and landing.”

Of course, Telespazio VEGA Deutschland is not a hardware provider and worked as part of a dedicated consortium set up by DLR for the hardware procurement. While procurement support is not new to the company, starting to work on an asteroid mission and beginning with the hardware was indeed a unique experience for the team!   

On-board software for the “shoebox”

Although MASCOT is a very small payload that resembles the shape of a shoebox, the inside is like a Swiss watch, all almost impossibly packed, with four different instruments, a redundant architecture for the OBC, a transponder, a power control and distribution unit, batteries, a variety of sensors for attitude measurement and a mobility mechanism, allowing MASCOT to re-locate once on the asteroid, by jumping like a frog.

All this needs to be controlled by the OBC and the data processed, compressed, stored and transmitted to the mother spacecraft when visible. Mission autonomy is an important requirement as, once landed, MASCOT will be alone, with reduced or no commanding capability from the ground.   Johan and José who worked with Federico on the on-board software were part of this challenge, to develop the on-board software fitting all the user requirements.

This was the System Engineering part,” adds Johan. “We had to collect the user requirements from the DLR System and Operations teams, the scientists and the providers of all subsystems to ensure that the on-board software fits all their demands – which might interfere with one another.”

Today the on-board software is ready to use, though it is foreseen to improve and tune it for the final asteroid mission. This will be done during the cruise phase to the asteroid, which will be lasting less than 4 years.

A simulator that is more than a simulator

Only two years ago, another team member joined: Eduard Baumstark was to develop the Software development & validation facility (SDVF). The SVDF is a virtual model of the lander and includes the on-board computer and all MASCOT instruments, equipment models, systems, communication and data links.

The SDVF was specifically designed to help my on-board software colleagues,” he tells us. “While MASCOT was being built, we needed to be able to test and validate that the OBC software under development by our team were working. With the SVDF we could replace the hardware elements that were not yet available with the simulation models, even the OBC itself!  With dedicated hardware interface cards, the SDVF allowed later to run functional, performance and robustness tests with the OBC hardware-in-the-loop.”

But in the meanwhile, the SDVF developed into even more: The DLR AIV team in Bremen, integrating and testing the MASCOT lander could use it as an EGSE, short for Electrical Ground Support Equipment. This is thanks to the test scripting capabilities of the SDVF, its hardware interface cards and also to a Central Check System based on SCOS2000 (ESA Mission Control System Software). 

The EGSE is normally used for testing hardware subsystems while the SDVF was initially targeted at the on-board software development and validation only. But if it can be reused, why not?” says Eduard with a smile.

Walk on the asteroid

The SDVF is planned to be used to simulate end-to-end ‘walking’ scenarios on the asteroid, providing sensor stimuli to the MASCOT flight spare model, which will be used as ground reference model in the near future,” adds Johan at the end. “But for me it has already been quite an end-to-end adventure. We started with a small piece of hardware, added the software. Once more and more elements were built around by the various parties it became a full picture of what we are actually involved in. What we contributed as individuals is a little bit like ‘walking’ on an asteroid!

All the names of the contributors of the MASCOT mission, whether they are hardware or software engineers, have been engraved on a small plate that is attached to the lander. “That’s really end-to-end,” closes Federico before he rushes off to his next meeting.

About MASCOT

MASCOT is a DLR payload on board the Japanese Hayabusa2 spacecraft. It launched from Tanegashima Space Centre on 3 December 2014. The target of this mission is to land on the asteroid 1999 JU3 and perform in-situ measurements.

These will help to increase our knowledge about the formation of our solar system. It will take HY2 less than 4 years to reach the asteroid 1999 JU3. To save energy, MASCOT will be switched off most of the time, but activated at regular intervals by the team of the MASCOT control centre at DLR for checkout and calibration purposes.

Thumbnail: Copyright DLR 


Further Links

Watch Hayabusa2 Launch (JAXA)DLR Space BlogDLR MASCOT page

SimulationOn-board software –  Sites: CologneRosetta involvement - Rosetta and Philae photo gallery


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