Are there any technical details available? It would be super interesting to see all the stuff that is re-developed from old specs, and to see how all the calculations and commands fit together to reach thw mission goals, or even what the received data and telemetry looks like.
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?
I doubt it's more complicated than knowing the language and having the proper transmission hardware. 1978 seems a little early to be worrying about hacks of that variety. That said the hardware could also have some kind of encryption built in. I'll ask if I get a chance, though - I hope to get some details from the project soon.
> Arecibo is the only thing big enough right now.
Not entirely true. How did they control it in the 1970's?
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.
Very true. Keep in mind, though, higher power is more expensive.
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. :)
If they do manage to fire the engines, it has to pass through the lunar shadow on the way back to Earth and as it's running off solar panels this means a total shutdown, which it's never done before (alas, the uptime!). Let's hope it comes back up!
After more than 30 years I'd have to consider any batteries suspect... Much less ones that spent their time in space.
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.
According to that article, it also lost power briefly for the same reason during a set of maneuvers that were used to repurpose it decades ago, so it's not the first time this problem has come up either.
There was an article linked here a while back on the guy who designed that trajectory. It was completely intentional that ISEE3 would eventually return for further usage.
The trajectory designer was Bob Farquhar. He's been involved with the space program since the late 1950s. An amazing guy. Here's his recently-published memoir:
The Arecibo observatory has the world's largest radio telescope. They're very well known -- while they've been involved with a lot of space research, they're particularly famous for being the transmit site for the Arecibo Message:
I don't really understand why this page reports the received power in kW? This will inevitable result all reported power levels be some 10^-p with p > 3.
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.
by 1981 or so the acoustic coupler was antiquated. The modem had a controller that handled telephony stuff like dialing, hanging up, etc and a you'd just plug your POTS rj-11 straight into it.
My very first modem was a 300bps box that plugged straight into the phone line. I remember being frustrated that I could read faster than the text came in, even though I was only 8 years old or so at the time. When we got a 2400bps modem, it was fantastic that stuff came in faster than I could read it.
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.
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?
Computer hacking (I know, I know, "cracking") is not THAT common a topic in XKCD - I'm sure Randall knew 1337 was coming up and chose a relevant comic to use that day.
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?