19 May 2009
For the first time in spaceflight history, a satellite has used mobile phone technology to radio back to Earth. The transmission took place on 16 May when Herschel used the same technology as used in GSM mobile phone networks to send test data to ESA's deep space tracking station at New Norcia, Australia.
At 14:00 CEST on 16 May - just under two days after launch - Herschel switched its telemetry downlink to 'high rate mode' and began transmitting, marking the first-ever use of Gaussian Minimum Shift Keying (GMSK) modulation in space. GMSK is commonly used in Global System for mobile Communication (GSM) mobile phone networks due to its very efficient use of bandwidth and power.
"Herschel's 1.5-Mbps test transmission - roughly the same data rate provided by a home broadband Internet connection - was picked up at ESA's ESTRACK station at New Norcia, Australia, on Saturday, as the satellite was travelling some 280 000 km from Earth," said John Dodsworth, the Herschel-Planck Flight Operations Director speaking in the Main Control Room at ESOC, ESA's European Space Operations Centre, Darmstadt, Germany.
New Norcia: ESA's first 35m deep space station
During their missions, the GMSK-based radio links will be used by both spacecraft to transfer data gathered by their scientific instruments and on-board subsystems, providing information on flight status and overall health.
Herschel's successful operational test confirms results obtained during mathematical simulations and ground tests conducted since 2001, when the GMSK implementation on Herschel and Planck was first planned.
Plot showing Herschel's mobile phone call received at New Norcia station