The MIRAS instrument on ESA's SMOS satellite, launched earlier
this month, has been switched on and is operating normally. MIRAS
will map soil moisture and ocean salinity to improve our
understanding of the role these two key variables play in regulating
Earth's water cycle.
"Following the switch-on, MIRAS is working beautifully well with
all key subsystems, including all of the receivers, the optical
fibres and the correlator unit, in perfect functioning condition,"
said ESA's Manuel Martin-Neira, SMOS Instrument Principal Engineer.
"We have been able to produce reasonable test data even without
in-orbit calibration."
MIRAS (Microwave Imaging Radiometer using Aperture Synthesis) is
an L-band radiometer with 69 receivers mounted on three deployed
arms to measure the radiation coming from Earth.
In order to measure accurately, the receivers must be within a
+/-3°C temperature range of each other, with the optimal operating
temperature at 22°C. Heaters are installed on the satellite to
achieve the temperature needed.
Switching on the instrument begins with activating the central
payload computer, which controls many of the instrument's subsystems
and gives instructions to the distributed command and monitoring
modes on each arm.
To assess the electrical performance of the instrument after
switch-on while limiting the consumption of heater power, the
physical temperature for start up was set to 10°C.
"The active thermal control is now in operation and is keeping
the instrument well within the expected temperature range," Mr
Martin-Neira said. "Tomorrow we expect to assess the payload at the
final 22°C temperature."
The central payload computer also controls the 'mass memory',
which collects all the science data from the receivers and sends
them to receiving stations on the ground. The high-speed downlink,
which transmits the data to the ground station, was switched on, and
data have been transmitted to ESA's European Space Astronomy Centre
(ESAC), in Villafranca, Spain. The data acquisition and processing
systems located at ESAC are also working well, and the first test of
the product generation system has been successful.
"With the critical launch and early orbit phase completed, the
engineers can now evaluate the quality of the downlinks and
concentrate on the calibration of the instrument," SMOS Project
Manager Achim Hahne said.
Data provided by MIRAS will be important for weather and climate
modelling, water resource management, agriculture planning, ocean
currents and circulation studies and forecasting hazardous events
such as floods.
"We are very happy that we have received the first data from
MIRAS, which we expect to make very strong contributions to
scientists' understanding of Earth's water cycle," said Guillermo
Buenadicha, SMOS Payload Operations Engineer at ESAC.
"We are now looking forward to analysing the first data and to
start testing the processing systems in the ground station," SMOS
Mission Manager Susanne Mecklenburg said.
The SMOS (Soil Moisture and Ocean Salinity) Earth Explorer
satellite and ESA's Proba-2 were launched into orbit together from
the Plesetsk Cosmodrome in northern Russia on 2 November.
SOURCE: European Space Agency