Daniel Scuka from the European Space Agency
Part of the show Naked Science Questions and Answers
Chris - There's mission called Venus Express which is going to meet our near planetary neighbour, Venus. Already in the series, we've heard how Venus has a runaway greenhouse effect and also we want to find out if there are active volcanoes on the surface. Well this week, in part three, we're going to be catching up with Kris Capelle about ESA's worldwide network of ground tracking systems. Here's Daniel Scuka, who brings this report from ESA.
Daniel - Venus Express is a fantastically advanced spacecraft and in April it will enter into orbit around Venus with seven sensitive instruments to gather a wealth of data. But that data has to be transmitted to Earth and throughout the mission, telecommands and instructions must be radioed up from the ground. This is where the European Space Agency's worldwide ESA Tracking Ground Station Network comes into action. ESA maintains eight stations in the ESTRACK network, located in Spain, Belgium, Sweden, South America and Australia. Earlier this week Kris Capelle, Venus Express operations manager, was in the main control room at ESOC, participating in an intensive simulation exercise.
Kris - The stations are controlled locally from ESOC so we do remote control of the stations, except for critical operations like the Venus orbit insertion.
Daniel - The ESTRACK system comprises six stations having smaller 15 metre antennae and two deep space stations with giant 35 metre antennae. These latter two are located in New Norcia, Australia and Cebreros, Spain. Venus Express is being telecommanded via the 35 metre station in Cebreros, which is the newest station to join ESTRACK. Having been completed in September 2005 on the site of an old NASA Apollo tracking station. The Cebreros ground station communicates with Venus Express at X-band gigahertz radio frequencies.
Kris - For Venus Express we're using eight gigahertz. It's about eighty times more than a normal radio station
Daniel - But die to the Earth's rotation, the station can only send telecommands or receive data when Venus Express passes overhead. As a result, the spacecraft gathers data in a store and dump mode; storing precious science data on board in a twelve gigabit memory array until it can contact Cebreros for download. During the upcoming and risky Venus Express orbit insertion, the spacecraft will be 125 kilometres from Earth and it will take radio signals travelling from Cebreros at the speed of light, six minutes and 46 seconds to reach the spacecraft. I asked Kris how many missions ESA is currently controlling from ESOC.
Kris - We have 14 satellites flying. We have scientific satellites like XMM, and we have our Earth observation satellites, and then we have our deep space satellites like Venus Express, Mars Express and Rosetta, and Smart 1 around the Moon.
Daniel - During next month's orbit insertion, the X-band antenna on the spacecraft will not be facing Earth. Only the smaller and weaker S-band antenna will. So ESA has asked NASA to help out.
Kris - They have 70 metre dishes and for some deep space missions we are requesting their support just to get some additional coverage or communication with the satellite.
Daniel - Join us again next week for a report direct form ESOC's main control room when we speak with the veteran ESA flight director on the high tech drama that takes place here during launches, orbital manoeuvres and landings. For the European Space Agency, I'm Daniel Scuka reporting from the European Space Operations Centre in Darmstadt, Germany.