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Interplanetary Network (IPN) Tested
CETS writes "Slim on detail but...USA Today reports of the first test of an Interplanetary Network. 'In a sign of cosmic communications to come, last week mission controllers sent signals to a Mars-orbiting European spacecraft, which relayed the instructions to NASA's Spirit rover on the surface, and a signal was returned to Earth back along the same path.'" NASA also has a press release.
VPN = Virtual Private Network
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By dong this they have already been able to increase the bandwidth to the rovers by x5.
RTFA
The IPN and the Internet are two different things.
The IPN does not use TCP or another transmission control protocol because it is simply not possible to acknowledge data/rerequest data if the latency is that big (minutes to days in the solar system).
This will be the case for the next Orbiter (Mars Reconnaissance Orbiter 2005) and any others prior to the Mars Telecommunications Orbiter which has a primary objetive of being a proper telecoms relay. MTO will provide at least 10x the current bandwidth, communication windows up to 8 hours in duration and will use optical as well as S-Band\X-Band radio links.
A phased array is composed of a large number of simple antennas in a regular pattern. Each of the simple antennas is connected to a phase controlling element, usually controlled by a computer. By adjusting the phase of each simple antenna, the array's radiation pattern can be manipulated to form one or more directional beams, without having to move any mechanical parts.
For NASA's application on TDRS, it allows them to simultaneously track and communicate with multiple satellites in low-Earth orbit, with a single electronically steered antenna system.
The trick NASA pulled with the phased array antenna on TDRS was to take the phase controllers off the spacecraft and put them at the TDRS ground station. The TDRS spacecraft takes the output of all the simple antenna elements and retransmits each one to the ground station. The ground station has a magic phasing/combiner box that takes the outputs of all the simple antennas and adjusts the phase of each signal and combines them under computer control. This splits the phased array into two parts, with part in space (simple antenna array) and part on the ground (phasing/combiner/control computer). This removes a big chunk of hardware and complexity from the spacecraft and relocates it to the ground station.
Looking at the TDRS web page, the latest series of TDRS spacecraft (TDRS-H, I, J) have the beam-forming hardware on board the spacecraft, instead of doing it on the ground.
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From their website...
The data rates from the Mars Surveyor to Earth are 1105, 2856, and 9240 bps and realtime rates are 29260 and 63580 bps.
That's not Wesley. This is Wesley.
== Jez ==
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Likely somewhat less. Geostationary comsats spend much of their fuel counteracting the effects of the Moon, which tends to pull them out of place. There is no moon around Mars that's large enough to cause problems. On the other hand, Mars os far enough away that it take s bunch of fuel just to get there.
By the way, the GPS network does NOT use geostationary staellites - they are in "half-Geo" orbits; the problem with getting the equivalent of a GPS network around Mars is that you'd need ~24 satellites. The GPS net is a big constellation.
Human genome = 3 billion base pairs = 6 GBit. Windows + Office = 20 Gbit. Which is more impressive?
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Could you provide some evidence to back that statement ?