ESA's Herschel calls home using mobile phone technology (Forwarded)

ESA News
http://www.esa.int

19 May 2009

ESA's Herschel calls home using mobile phone technology

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 [1200 UTC] 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.

In a typical GSM mobile phone network, the same technology transmits data at
a somewhat lower speed. Herschel's sister spacecraft Planck also uses GMSK
technology, and its transmission capability will be tested later during the
satellite's commissioning phase.

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.

The development was driven by the need to use bandwidth more efficiently in
view of the growing number of ESA missions that require X-band
communications via the Agency's deep space ground stations. Gaia, scheduled
for launch in the 2011 timeframe, will also use GMSK-based communication.

The GSM standard is the most popular modulation standard for mobile phone
networks in the world. According to the GSM Association, terrestrial GSM
networks now cover more than 80% of the world's population in more than 212
countries and territories -- and will soon extend 1.5 million kms further to
L2, Herschel and Plank's final orbital destination.

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