The first-ever reception of signal took place at ESA's new 35m deep space station at Malargüe, Argentina, on 14 June. There's still a lot of work to be done to have the station fully comissioned, but this is an excellent achievement and an important milestone - and the signal came from our very own Mars Express, orbiting the Red planet some 193 million km away.
Roberto Maddè, the DSA-3 project manager, wrote:
We did a test 'shadow tracking' of Mars Express last week on 14 June, around 22.30 UTC.
The signal in L-band is shown in the picture (at left). We measured a signal/noise ratio of about 56 dBHz, which matches the levels obtained by ESA's existing 35m station at Cebreros during the same pass.
Pointing still needs to be optimised (pointing correction for our test was done manually); these tests are still 'qualitative'.
Some quantitative tests (less news-worthy but more useful to understand whether the station is operating within specs) are being done and look promising.
Now, the teams on site are recalibrating the beam waveguide mirrors; we'll have more tests in two weeks. But we need to calibrate the pointing first.
DSA-3 is set to enter regular service later this year.
On Sunday, 9 January, Mars Express will make its closest approach to Phobos, with the spacecraft passing just 111 km above the moon's centre at 14:09 UT (15:09 CET). Of course, we all know that science is about a lot more than pretty pictures; but we can’t help ourselves can we? The first question any of us ask when we hear about a new flyby is, "When do we get the images?" We want to see Phobos, and we want to see it now!
While closest approach takes place this coming Sunday, Olivier Witasse, ESA Project Scientist for Mars Express, explains below that all things come to those who wait. I asked him when we can expect the first image? Olivier replied:
We will have to be patient! The whole Phobos data set will be downloaded to Earth by Tuesday, 18 January. The HRSC team will then process the data, and we can expect a release of images (including a 3D view) on Friday, 21 January.
Why wait for nine days after the closest approach?
The reason is that besides this Phobos event, there are other camera observations of Mars and many observations by the other Mars Express instruments. Software plans and optimises the data downlink to make sure that no instruments lose any data, and it uses the biggest data storage on board (the one for the camera) to act as a buffer when downlink capabilities are scarce. This avoids overwriting valuable data! Once the other data are safely on the ground, then Mars Express sends the camera files.
An interesting aspect of this story is that starting on 19 January, contact with Mars Express will be much reduced for five weeks. We will even loose contact for some days due to the solar conjunction, when the Sun will block our view of Mars and Mars Express. During this period, the spacecraft will be fully autonomous but perform no observations. Luckily, the Phobos close encounter occurs more than a week before and its images will be on the ground just in time! -- Stuart
Note: To help pass the time, enjoy are a pair of recent images captured in March 2010 by the HRSC.
These close-ups of the surface of Phobos were taken on 10 March 2010 at a
distance from the moon's centre of 278 km, with a spatial
resolution of about 3 m/pixel. The images are available in the Planetary
Science Archive. Credit: ESA/ DLR/FU Berlin (G. Neukum).
A short video clip recorded 9 March 2010, 19:50 CET, showing ESA's giant 35m deep space antenna at Cebreros station (Spain) - part of the Agency's ESTRACK network - swinging into position to start a ground station pass. The weather tonight in central Spain is crystal clear and cold (below freezing) - perfect!
CEB was used last week to track Mars Express during Phobos closest approach... -- Daniel
Greetings again to all Phobos and Mars aficionados!
Christian Andreas Doppler (29 November 1803 – 17 March 1853)
The closest-ever flyby of Phobos to date will be dedicated to an experimental method called 'radio sounding'. The way radio sounding works is that we place the object (think a celestial body) we want to investigate close to the trajectory of a moving vehicle (think a spacecraft) equipped with a very stable and precise radio transmitter. We also need a very sensitive receiver equipped with measurement devices to record the received signal (think ground stations). The transmitter on the moving vehicle sends out a continuous unmodulated signal (meaning no actual data will be transmitted - just an 'empty' carrier signal). The receiver receives the signal and then sends that signal to the measurement equipment, which will record the famous Doppler shift of the received signal's frequency (access more details under the 'Full story' link below) -- Hannes.
NASA's Deep Space Network (DSN) will play a critical role in the central science activity for the 3 March flyby.
The American space agency's giant 70m station at Robledo, Spain (DSS-63), will be enlisted to track ESA's Mars Express during Phobos flyby to record extremely precise Doppler data - which in turn will enable Mars Express scientists to obtain the best-ever measurements of Phobos gravity and hence mass (click on 'Full story' for more details). -- Daniel
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Greetings again to all Phobos and Mars aficionados!
