Santiago comes online
15 February 2001An extra facility has been added to the network of ground stations used to control XMM-Newton. In addition to Perth and Kourou, flight controllers at the European Space Operations Centre in Darmstadt are now also using a station in Santiago, Chile, to communicate with the spacecraft and receive its science data.
The new station, belonging to the University of Chile, has been added to increase and safeguard coverage by the two principal stations in French Guiana and Australia which have been used from the start of the XMM-Newton mission. Tracking facilities at ESA's VILSPA facility near Madrid remain as a backup, particularly during the eclipse seasons.
The stations in Perth and Kourou have, to date, ensured communications with the satellite for practically the entire duration of each 48-hour orbit. The only times they could not "see" the satellite were as it passes closest to Earth (perigee) - but no science observations are ever conducted then because of radiation constraints - and at its furthest (apogee) when a short one hour break in the science observations was necessary.
Ensuring coverage during this "apogee gap", Santiago will greatly improve the mission's efficiency, particularly for science observations. Staff at the XMM-Newton Science Operations Centre at VILSPA near Madrid will have greater planning flexibility.
Principal Investigators and other astronomers using the X-ray telescope heartily welcomed the news, when they were told at the recent Science Working Team meeting at VILSPA that the first data from the satellite had effectively been received there the previous night. And by a remarkable coincidence, the target being observed during this apogee passage was a very bright active galactic nucleus, ESO 198-G24, which was originally discovered using one of the instruments at the La Silla facility of the European Southern Observatory, coincidentally also located in Chile!
Visibility of the satellite from Santiago is similar to that from Kourou and this brings an additional advantage. The Diane tracking station in French Guiana had in the past frequently been obliged to remain in silent mode for XMM-Newton (only receiving data) on the occasion of Ariane launches or when the Diane facility was used to place satellites into their final orbit (LEOPs). Santiago will now be able to act as a backup for Kourou whenever the need arises.
"This reinforced coverage with the Santiago station will greatly help our own team in their day-to-day operations of the spacecraft," says Dietmar Heger, XMM-Newton Spacecraft Operations Manager at ESOC. "But the astronomers will gain most. With the elimination of the apogee gap, our colleagues at VILSPA will be able to schedule even more long-duration observations and compensate for the constraints imposed by the higher than expected radiation levels which the mission has experienced."
The Santiago facility, situated 28km from the Chilean capital, is equipped with half a dozen antennae. It has participated in many international space missions. ESA has used it as a backup station for Ulysses and when the ERS satellites were launched. The XMM-Newton mission will use the largest dish, a 12m receive-only, and a 9m transmit-only. Associated equipment installed for the X-ray observatory will also be used for the early orbit phase of the ENVISAT mission, when it is launched later this year.