Rover Relay upgraded to 256 kilobits/sec. Congratulations - and how?

Hi,

I have read that the people working behind the Mars missions, appear
to have successfully upgraded the Mars Relay to transmit at 256
kilobits/sec, allowing approximately 250 megabits worth of data to be
transmitted in a single relay session. (I'm speaking only of data
rates from Mars Surface to Mars Orbit.)

I have also read several documents on the Net, including some old
1990's specification document on the Mars Global Surveyor relay
antenna. It gave me the idea that the data rate was limited to
around 128 kilobits per second.

This harkens back to a bandwidth-upgrade accomplishment that I
remember well. In the 1990's, I recall the breakthroughs that were
necessary in order to cram data through Galileo's low gain antenna at
Jupiter, after the high gain antenna failed to open after repeated
attempts. If I remember correctly, the 16 bits/sec (max) low-gain
antenna was upgraded well beyond spec via software to perform up to
160 bits/sec (max) uncompressed rate, plus various compression
algorithms (both lossy and lossless) were implemented, to achieve the
equivalent of approximately 1 kilobits/sec rate average. The literal
engineering accomplishment of a very difficult "cramming as many
elephants as possible through a drinking straw as quickly as possible"
problem, so to speak.

I would like to ask -- how was the relay bandwidth upgrade
accomplished, considering the original specifications appears to have
permitted 128 kilobits per second? Was a provision added for 256
kilobits per second relay just in case it was found to be possible, or
was this a software accomplishment that allowed the specs to be
extended while the probes were already in orbit? New
modulation/codec algorithm? Hand-optimized clock-cycle-exact code?
Power supply modulation to antenna? Turning off other instruments to
give enough power for the higher data rate? (Just being wild on
unorthodox ideas that might have been invented to exceed an antenna
system spec -- I am not in the space industry myself but have a basic
understanding of various concepts like these.)

This also leads to another interesting question -- How much room is
there for further improvement? Would an upgrade to 512 kilobits/sec
and 1024 kilobits/sec be theoretically possible using any of the
existing orbiters, especially if a future surface mission had a
theoretical aimable UHF antenna dish that tracked the relay satellite?
Are the satellites theoretically flexible enough to support even
higher data rates for future missions of any existing orbiter
(Surveyor/Climate/Express as of 2003), assuming their missions were
extended to cover such a theoretical future surface mission?

Don't be afraid to be technical; I'm a software engineer here,
although not in the space industry.

Mark Rejhon
www.marky.com (personal webpage)

If nothing of the kind of upgrade you suggested has occured, I belive the
rate was accomplished with the Odyssey orbiter as both the MER rovers and
that orbiter fully supports 256 kbps.

Sincerely
Bjørn Ove

(Mark Rejhon) wrote in message
(Surveyor/Climate/Express as of 2003), assuming their missions were
extended to cover such a theoretical future surface mission?

Correction; I meant Odyssey instead of Climate Orbiter.
I meant the three active orbiters, Surveyor/Odyssey/Express.
(I know Climate Orbiter got lost due to a metric confusion.)

Thanks,
Mark Rejhon

In article ,
Mark Rejhon wrote:
This harkens back to a bandwidth-upgrade accomplishment that I
remember well. In the 1990's, I recall the breakthroughs that were
necessary in order to cram data through Galileo's low gain antenna at
Jupiter, after the high gain antenna failed to open after repeated
attempts. If I remember correctly, the 16 bits/sec (max) low-gain
antenna was upgraded well beyond spec via software to perform up to
160 bits/sec (max) uncompressed rate, plus various compression
algorithms (both lossy and lossless) were implemented, to achieve the
equivalent of approximately 1 kilobits/sec rate average. The literal
engineering accomplishment of a very difficult "cramming as many
elephants as possible through a drinking straw as quickly as possible"
problem, so to speak.

When they originally announced plans for the low-gain antenna
Gailleo mission, 3 techniques were emphasized:

- improving reception by arraying DSN antennas and installing more
sensitive receivers.
- lossless and lossy data compression for non-imaging and imaging
data, respectively.
- better ECC allowing higher data rates and lower error rates.

AIUI compression is pretty standard on contemporary missions.

Jon
__@/

Also some things can be upgraded, cause the chips are EPROM,
electronically programmable memory and like chips that can be changes
within reason.. Like how some newer BIOS can be changed by a program.

Mike


Jon Leech wrote:

In article ,
Mark Rejhon wrote:
This harkens back to a bandwidth-upgrade accomplishment that I
remember well. In the 1990's, I recall the breakthroughs that were
necessary in order to cram data through Galileo's low gain antenna at
Jupiter, after the high gain antenna failed to open after repeated
attempts. If I remember correctly, the 16 bits/sec (max) low-gain
antenna was upgraded well beyond spec via software to perform up to
160 bits/sec (max) uncompressed rate, plus various compression
algorithms (both lossy and lossless) were implemented, to achieve the
equivalent of approximately 1 kilobits/sec rate average. The literal
engineering accomplishment of a very difficult "cramming as many
elephants as possible through a drinking straw as quickly as possible"
problem, so to speak.

When they originally announced plans for the low-gain antenna
Gailleo mission, 3 techniques were emphasized:

- improving reception by arraying DSN antennas and installing more
sensitive receivers.
- lossless and lossy data compression for non-imaging and imaging
data, respectively.
- better ECC allowing higher data rates and lower error rates.

AIUI compression is pretty standard on contemporary missions.

Jon
__@/