I heard a message from Space Shuttle Atlantis today that got me wondering:
I can use Skype or Windows live messenger and have clear conversation with people on the other side of the globe, but NASA, with all of its space-age technology, still sounds like they’re communicating on a tinny transistor radio from the Apollo days. Why can’t they transmit/receive communications with the space shuttle using a digital stream or something else that doesn’t sound like a walkie-talkie from Toys ‘R’ Us?
Any communication you do on earth travels mostly through wires. Even cell phone signals only go via air to the nearest tower, then go by wire to their destination (or to another tower then by air again)
The space shuttle, last I checked, lacks a hard wired connection to the telecomm network.
The amount of atmosphere the shuttle signals go through makes some static a surity.
They probably are communicating through equipment from the Apollo days. The shuttle was designed in the 1960s. As with any government-owned piece of equipment, upgrades are piecemeal and typically are applied to important pieces of equipment. Not that a radio isn’t important, but if it works it probably doesn’t need to be replaced. Hell, the plane I fly on has equipment from the 1950s on it, because it works dependably and almost never breaks.
Even if they did use newer equipment (which they may well do), they still face bandwidth limitations. SATCOM from an aircraft at 25,000 feet sounds exactly the same as the shuttle comms. I wouldn’t expect a marked improvement from that any time in the near future.
From my understanding, any hardware that goes up into space needs to be hardened against radiation and the forces of lift off. That is why they say some thing like the ISS only has the computing power of a home PC in the entire station and the moon lander had the computational power of a graphing calculator. There is a lot of research and testing to make sure that equipment works in space. Another thing is that I believe that almost all the computer code is custom. I would not want a PC to crash while I am dodging a meteor.
Houston, we have a problem. I just got the Blue Screen of Death…
analog radio has lots of benefits. you can communicate an intelligible message with noise and low signal levels that you can’t digitally. analog voice with compression can convey all the needed information and yet not be high fidelity.
The stuff that gets sent into space has been in use forever and its reliability is well known.
Cap’n: “Lieutenant, why can’t I raise Houston on the Spacecom 9000?”
Lt: “Sorry sir, it locked up, I’m going to try to reboot it.”
Here’s an actual NASA link detailing the comms and on the space shuttle…
http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-jsc-comm.html#sts-comm
I think the main issue is movement since the shuttle is moving pretty fast in relation to the ground unless it assumes a geostationary orbit. This causes a Doppler effect which is the cause for the way it sounds. But, that is only with analog transmission. Digital transmission, which the shuttle does in fact have for voice, data, and video, can solve this problem.
The article mentions UHF which is old school, S-Band, which is pretty old school, C-Band which is newer, and K-Band which is really new. In terms of SATCOM that is, for something like the space shuttle which probably has some serious mission critical requirements. So, the equipment is obviously updated.
Back in the day and they still do as HAM clubs talk to them, they used HF.
Hams communicate with the shuttle on VHF. I was a member of a club that set up the equipment for a school in St. Louis do a shuttle communication a few years back.
The ISS communicates with school kids regularly.
The ARISSpage gives you all the info you need on the program.
If you are a Ham (or know one), they should have the equipment and can help you tune in and listen. They use VHF (2 meter) frequencies.
A scanner might work, but not with the standard antenna.
Some more information can be found here.
You’ll need a more sophisticated receiver or scanner to pick up chatter between the shuttle, ISS, and ground control. The frequencies can be found here.
It helps to know when the kids are overhead, so try hereor hereto plot those magnificent men in their flying machine…
Currently, Atlantis is docked with the ISS, and is actually planning on installing 2 new amateur radio antennas on the Columbia module to improve ham communications.
Find a ham in your neighborhood and see if you can make contact. It’s an awesome achievement I’ve accomplished only once.
From a first principles point of view the shuttle isn’t a trivial problem. As pointed out above, the thing moves, and fast. Also, even when it is directly above, it is still 300 miles up. That is a long way for a radio signal to go. Especially given the small size of the antennas available, and since it is moving, the low gains possible.
Your cell phone signal travels a few miles. Ideally the signal drops off with the square of the distance. So in comparison the Shuttle’s actual signal strength available isn’t going to be exactly huge.
The limiting factor for the quality of communication is the information rate. This is the product of the bandwidth of the signal and the signal to noise. We have seen how the signal strength can drop. The noise is essentially impossible to reduce, and we are left with the bandwidth of the signal. If you use a simple analog radio - i.e. AM or SSB, or a standard narrow band FM, the bandwidth is fixed. And that is about it. Higher quality communications must increase the information rate. And that means at least one of: wider bandwidth, more signal, less noise. Digital communications are identical. It is just another form of modulation. Your GSM mobile phone has exactly the same issues. It is just that digital has rather more brutal failure modes. Breakup of the sound, garbling, total dropout. Whilst analog just gets noisier and harder to understand. But humans being what they are are better at hauling meaning out of a very noisy analog signal than a juddering, breaking up, stuttering digital signal. Even if the overall information content is the same.
When you want ot run a safety critical system, you want the simplest and best proven technology for your comms. There is no gain to be had going to a more complex system, and considerable risk.
I discount all the theories about fears of a new system breaking down because the old system can be kept as backup, but Voyager transmitted pristine pictures although it as lauched in the late 70s. Are you saying that shuttles these days can’t transmit at a bitrate fast enough to give a clear signal? If so, how does dish TV work?
IIRC, the Voyager video was time delayed because it took longer than real time to transmit the full-resolution images.
Taken to an extreme, it would be possible for me to mail a high-definition picture to you one pixel at a time. It would just take a few million postcards, each with something like x=3506, y=10492 color=2eo5fd written on it, and it would then take you a lot of time to sort the cards and re-create the image. The net result will be a clear picture, but at the expense of a lot of time.
As for satellite TV, both the satellite and your antenna are stationary. In reality, both are moving pretty rapidly through space, but relative to each other, they’re bolted together. The Shuttle or ISS, however, are moving very quickly and very high over the Earth’s surface, so it becomes a bit of a race to squirt out a signal fast enough and strong enough.