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Rhea's contribution to saving the XMM X-ray telescope
Louvain-La-Neuve, Belgium, 10 November 2008 - During a two-week period in October 2008, the XMM spacecraft suffered two emergencies. Firstly, on 7th October, it entered its emergency Sun pointing survival mode. However, within a day, the spacecraft was back to normal operations. Then, on 18th October, contact with the XMM spacecraft was lost and the flight control team thought that they had lost the spacecraft forever. Two of Rhea's engineers contributed to saving the XMM X-ray telescope on these occasions: Mauro Pantaleoni and Rob Harris.
The XMM mission is a very exciting mission. The spacecraft, known as XMM-Newton, is the most powerful X-ray telescope ever placed in orbit. It carries three very advanced X-ray telescopes, each of which contains 58 high-precision concentric mirrors, delicately nested to offer the largest collecting area possible to catch the elusive X rays. These Mirror Modules allow XMM-Newton to detect millions of sources, far more than any previous X-ray mission.
The first emergency had been due to a single event upset switching off one of the AOCS units. This was recognised and the unit switched back on, but it had not been properly initialised. So when it was next needed, it failed to operate. However, the AOCS survival mode rescued the situation. Subsequently, having diagnosed the problem with Rob's help, the spacecraft was restored to full operation.
The second emergency had resulted in an RF switch settling into a "neutral" position between its two contacts, so disabling both the communications uplink and the downlink. Mauro is a member of the XMM Flight Control team and contributed with his expertise to analysing the different scenarios for the loss of contact and proposing solutions for re-establishing contact with XMM. It was decided to repeatedly command the RF switch to its correct position and, in the end, using sufficient uplink power, the command got through, the RF switch moved to its commanded position and the communications link was restored.
Mauro Pantaleoni is one of Rhea's AOCS engineers. After the recovery he commented, "The loss of the ability to command a spacecraft is one of the worse nightmares of an Operations Engineer, and it's exactly what we faced with XMM. The TM/TC link is the umbilical cord and the only way we have to keep in touch with the spacecraft. After almost five days of lack of contact, the fear of finally losing XMM was becoming real. Luckily a joint effort between the Flight Control team and Industry made the recovery possible."
Rob Harris is Rhea's senior AOCS engineer. He was the XMM AOCS architect and is currently responsible for the AOCS on the BepiColombo mission. In the past, he invented the strategy for recovering the SOHO attitude control after the near loss of the SOHO spacecraft in 1999, when all the gyros were lost - his strategy turned the entire spacecraft into a giant gyro. His AOCS survival mode design on XMM ensured the spacecraft's safety whilst the XMM recoveries were performed.
Rhea one of the main sponsors of the Fifth European Space Weather Week
Louvain-La-Neuve, Belgium, 5 November 2008 - Rhea System S.A. is pleased to announce sponsoring the Fifth European Space Weather Week.
The Space Weather Week will take place on 17-21 November 2008 in Brussels, Belgium. The objective of the event is to bring together the diverse stakeholders working on all elements of space weather. The topics to be discussed will cover a wide range of subjects:
- Space Weather and the European Approach to Space Situational Awarenes
- Global Navigation Satellite Systems: science, users needs and applications
- Offshore Drilling, Magnetic Surveying and Geomagnetic Variations: science, user needs and applications
- Space Weather Models: from research to operations
- New and Existing Data: catalogues, tools and services
- Solar Weather: new results, analysis techniques,
forecast tools and the outlook for users
The keynote speaker for this year's Fifth Space Weather Week will to be the ESA astronaut Dr. Christer Fuglesang. He is the first Swedish astronaut and flew on the Space Shuttle Discovery STS-116 to the International Space Station (ISS) on the 9th until 22nd December 2006. During his mission he participated in two spacewalks for attaching hardware to the ISS and reconfiguring the Station's electrical power system. Dr. Fluglesang is assigned as a Mission Specialist on board the Space Shuttle STS-128 due to fly on 30 July 2009 to the ISS.
"The European Space Weather Weeks are a key event in the European Space Weather calendar," said Alexi Glover, one of Rhea's space weather scientists and co-chair of the meeting. "This is the fifth in a series of annual workshops that aims to bring together scientific applications and user communities working on space weather in Europe. This is the third time the event will be held in Brussels. We are also delighted to welcome Dr. Fuglesang to this year's meeting who, as well as being an ESA astronaut, is an expert in experimental particle physics and will no doubt give a fascinating keynote lecture."
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