Data transmission from MARS
Mon, 2005-01-17 23:18 — admin
You've to look back to early 90's to understand how the spectacular images we now get from rovers on Mars are REALLY beamed back to Earth... 
MER: Mars Exploration Rovers: Spirit and Opportunity
They've both safely landed on Mars
Their landing site has been photographied by MGS (Mars Global Surveyor).
Spirit site
Opportunity site
Opportunity is quite well-named because it landed right IN a small 22m-wide crater, providing scientists with a nice outcrop to study !
Software problems onboard Spirit have been solved and it's flash memory has been completely reformated.
It's nearly an OS "reinstall" from 150mio kms away...
Over the 200-250 MB of data both rovers send back to Earth each day, 80% of it is made via a 128kbps antenna called MR aboard MGS.
MGS passes 2-3 times per day over the rovers and, then send these data back to 20-60m-large antenna on Earth. These antennas form the DSN (Deep Space Network) extending from California to Spain and Autralia.
Remeber that DSN still "hear" the signal from Voyager 2. A singal as powerfull as a watch battery...
Voyager 2 is 10,852,000,000 Km away...
Status of Voyager spacecrafts
Back to data transmission:
MR is the antenna used for transmission in 2004.
According to This article, the MR has been designed buy a frenchguy of CNES back in 1987.
It was imagined for transmission of data from french (ballons on MArs) and soviet missions in a cooperative effort with US ones.
Another key element is that it CANNOT work as is (It has NO internal memory).
Hopefully there's a quite performant camera aboard MGS, it's called MOC (Mars Orbiter Camera).
It's able to on wide range of data rate transmission (from a few bps to over 40Mbps) and has about 86Mb of data storage space. It operates 3 camera, but emulate the MR as is it was a fourth one !
Then data from the MR are managed by the MOC system and stored in its memory.
IIt's quite amazing to know that:
1) The antenna used to beam us back the 2004 rovers images is from a 1987 idea of a frenchguy and integrated on the 1994-built MGS (10 years ago).
2) The datarate is quite high for such "old" technology, but the storage capacity is quite low...
Given the 2x200MB it has to send back to Earth each day and taken apart its own data, it surelly has to transmit during a good portion of the day
3) The rovers transmits at a rate up to 128Kbps (Max MR antenna rate).
They transmit to directly to Earth too, but I don't know the rate.
MER: Mars Exploration Rovers: Spirit and Opportunity
They've both safely landed on Mars
Their landing site has been photographied by MGS (Mars Global Surveyor).
Spirit site
Opportunity site
Opportunity is quite well-named because it landed right IN a small 22m-wide crater, providing scientists with a nice outcrop to study !
Software problems onboard Spirit have been solved and it's flash memory has been completely reformated.
It's nearly an OS "reinstall" from 150mio kms away...
Over the 200-250 MB of data both rovers send back to Earth each day, 80% of it is made via a 128kbps antenna called MR aboard MGS.
MGS passes 2-3 times per day over the rovers and, then send these data back to 20-60m-large antenna on Earth. These antennas form the DSN (Deep Space Network) extending from California to Spain and Autralia.
Remeber that DSN still "hear" the signal from Voyager 2. A singal as powerfull as a watch battery...
Voyager 2 is 10,852,000,000 Km away...
Status of Voyager spacecrafts
Back to data transmission:
MR is the antenna used for transmission in 2004.
According to This article, the MR has been designed buy a frenchguy of CNES back in 1987.
It was imagined for transmission of data from french (ballons on MArs) and soviet missions in a cooperative effort with US ones.
Another key element is that it CANNOT work as is (It has NO internal memory).
Hopefully there's a quite performant camera aboard MGS, it's called MOC (Mars Orbiter Camera).
It's able to on wide range of data rate transmission (from a few bps to over 40Mbps) and has about 86Mb of data storage space. It operates 3 camera, but emulate the MR as is it was a fourth one !
Then data from the MR are managed by the MOC system and stored in its memory.
IIt's quite amazing to know that:
1) The antenna used to beam us back the 2004 rovers images is from a 1987 idea of a frenchguy and integrated on the 1994-built MGS (10 years ago).
2) The datarate is quite high for such "old" technology, but the storage capacity is quite low...
Given the 2x200MB it has to send back to Earth each day and taken apart its own data, it surelly has to transmit during a good portion of the day
3) The rovers transmits at a rate up to 128Kbps (Max MR antenna rate).
They transmit to directly to Earth too, but I don't know the rate.