After its
successful launch into space last week, the Herschel Space Observatory used cell
phone technology to call back home the first time the technology has been
used in spaceflight.
Herschel and
its partner Planck were launched
in tandem aboard an Ariane 5 rocket from the European Space Agency's (ESA) Guiana
Space Centre in Kourou, French Guiana.
Herschel is
the largest, most
powerful infrared telescope ever launched into space. It will make
observations in the far-infrared to sub-millimeter wavelengths of light that
will allow astronomers to study cold, dark dust clouds and possibly star
formation in action.
At 12:00
GMT (8:00 a.m. EST) on May 16 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.
The
transmission sent send test data to ESA's deep space tracking station at New
Norcia, Australia.
"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 traveling some 280,000 kilometers
[174,000 miles] from Earth," said John Dodsworth, the Herschel-Planck
Flight Operations Director at ESA's European Space Operations Centre in
Darmstadt, Germany.
In a
typical GSM mobile phone network, the same technology transmits data at a
somewhat lower speed. 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.
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 some 1 million miles (1.5 million kilometers)
further to the L2 Lagrange point (a gravitational stability point in the
sun-Earth system), Herschel
and Plank's final orbital destination.
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