We Are Now In Command of the ISEE-3 Spacecraft
spacecollege.org
spacecollege.org
Or is this kept confidential to try to prevent outsiders from going at it like in that xkcd posted in the comments here? Or is the only "protection" based on the requirement to have access to those huge observatories?
Arecibo isn't like a public library or something. You can't just go in and start hitting buttons! They used it as the climax of a Bond movie!
Interesting, then, that the scenario already appeared in fiction by 1950 (in the Tintin story Objectif Lune/Destination Moon)
They chose Aricebo because it allows them to use very low power antennas to communicate. The size of the dish makes up for the lower power transmission.
In the past, they used high-powered antenna arrays.
For short pulses momentary power output reaches Terawatts!
They've said in the past (I'm failing to find the reference right now) that they chose Arecibo because of the high-gain of the antenna. I believe that the amplifiers that they're actually using above the dish are somewhere around 700 Watts.
Antennas with large effective apertures (of which Arecibo's is the largest) are considered high gain antennas, which have small angular beam widths. Friis' Transmission Equation shows that you could use low-power transmitters, but still maintain high boresight with a sufficiently large antenna surface. :)
http://spacecollege.org/isee3/isee-3-reboot-amplifier-instal...
It is an AR 700S1G4 with rated minimum output power of 700W, and will be used in S-band. Here's the datasheet:
http://www.arww-rfmicro.com/post/700S1G4.pdf
At these frequencies, the Arecibo dish has a gain of around 72dBi, putting the EIRP at about 7 gigawatts.
For scale, a typical wifi router has an EIRP of around 50 milliwatts, so this is about 140 billion times more powerful.
Considering it was meant to spend its life at L1 it may not have any batteries. Then again it also doesn't have a computer so it should be fairly robust.
On a related note, I also just noticed that the "Arecibo Radio Observatory" was in Goldeneye!
BITS not even BYTES, let alone kilobytes.
Bringing the conversation back to space, one of the first things we did with the modem was dial into some public NASA BBS (long distance!) and download pictures from Voyager.
I happen to see VGR1 pulling down data at "159.00 b/sec" right now.
Also Watt is not a very useful unit here. You want something like dB(mW) which is much handier to work with. Good thing is, you just have to look at the exponent to get a rough dB(mW) figure: 10·log_10(m) - (p-6)·10, p being the exponent, m being the mantissa; for a quick estimate let m = 5, 10·log_10(5) =~= 7. So for the p = -23 this gives about -167dB(mW), which is accurate enough.
I'd love to see some more technical details but according to this article:
http://www.planetary.org/blogs/emily-lakdawalla/2014/0207083...
Goddard claimed that they couldn't rebuild the hardware that was used to talk to ISEE-3 at reasonable cost.
The Space College project are using SDR: http://spacecollege.org/isee3/isee-3-reboot-project-status-a...
And they used their funding to buy some custom amplifier gear to send to Arecibo.
If NASA doesn’t have the money for it (or thinks they have better things to do with the money), they can’t do anything. The explanation of not having access to communications equipment is more about the cost of restoring that ability, not any claim that contacting the probe would in principle be impossible.
The message is more or less that they don’t just have some device standing around they can flip on and sit some intern in front of it for a few hours to get this going. NASA wanted to express that substantially more effort would be required.
It seems that many people (including people at NASA) are donating a lot of resources, time and money to this project. That’s why this can happen. But NASA can’t budget with the expectation of receiving donations.
Think of it like that old piece of software you wrote when you were young that you've since abandoned, because you know, about 20 years have passed, no one uses AppleII's anymore, 126 some odd other pieces of software that do exactly the same thing but better and faster have been released, and also mobile happened. Besides, you have a job now doing modern things for modern reasons that are actually valuable to people and the world and stuff, so really there's not even a reason to figure out how a 5 and a quarter floppy drive can possibly connect to your rMBP to have a look at the code and see if an emulator or whatever would make it run right.
But if someone wants to throw $151,000 in donations at it, sure kids, have a ball. And yeah, of course we'll reminisce and have some fun with it over a beer or two. Those were the good old days, after all, when we were real rocket scientists, and space probes Farquharing around the solar system on a perfectly choreographed dance of not just one mission, but three—no, not two, three—what do you think it's doing right now? You think this kind of thing just happens by chance? Have fun—and bring her back in one piece, will ya?