Australia down for scheduled maintenance: No talking to Voyager 2 for 11 months NASA is celebrating the return to full science operations of its ageing Voyager 2 spacecraft by not speaking to the thing for 11 months. After 48 years of service, the 70-metre-wide radio antenna in Canberra, Australia, is due a bit of TLC and will be undergoing upgrades for almost a year. Voyager 2, which is currently …
The '43' antenna in Australia is special in that is has an optional 400kW S-band high power amplifier, instead of the usual 20kW. A note from the manual (70-m Subnet Telecommunications Interfaces) states:
400kW Power Amplifier
2110 to 2118 MHz Only available at DSS-43. Cannot be used above 100 kW without special airspace coordination. No operation below 17 degrees elevation is allowed, no matter what the power is.
It is uncommon to see general HPA efficiencies above around 40% so they are looking at around 1MW of AC input power just for that amplifier when in use. The smaller 34m dish could be used, in theory, but they would need about 1.6MW of RF power, so around 4MW input AC to run it. And of course the RF route would have to survive 1.6MW without anything flashing over!
An antenna that size must have 60+dB gain, so pumping 400kW in would give you a very toasty 400GW ERP. That sounds crazy, are my numbers anywhere near right? If so I can certainly see why they don't want it running below 17deg elevation! I'm not sure wildlife flying into that (very thin, admittedly) beam would have time to notice it getting warm before they were turned into a puff of smoking plasma.
Very approximately, the power density from that antenna if you are behind the feed is never much more than around 104 W/m^2 which is high, but only about twice the generally regarded safe limit for human exposure at S-band of around 50 W/m^2 (compared to about 1kW/m^2 for full sunlight). Basically the 400kW from the feed is spread over the 70m diameter antenna's 3848m^2 area moderately evenly, then reflected back towards the satellite.
But that sort of power density will extend a long way out, and is very much higher than would be considered a normal test for any aircraft electronics system!
Well, it is. If it was *below* that limit, that would mean basically that they could turn the thing on without even thinking about it. Being above the limit means that they need "don't go inside while transmitting" fences, but being only 2x GRAS means that the hazard is pretty damn low and the area that needs to be controlled isn't that big.
As the crow flies, it is only ~10km away from Canberra's airport. Technically it's an international airport, but the international traffic is fuck-all. It is the major regional airport for about ~500k people (~400k in the city of Canberra, and another ~100k from surrounding towns/small cities).
"No operation below 17 degrees elevation is allowed, no matter what the power is."
According to NASA's DSN NOW page, the 43 antenna is currently st 10.40 degrees, and falling. It was at 10.80 when I first read your comment a couple minutes ago. (edit: It seems to have "bottomed out" at 10.38 degrees.)
https://eyes.nasa.gov/
https://eyes.nasa.gov/dsn/dsn.html
I think the limitation is on the use of the 400kW power amplifier, not the antenna. If it were me, I would be afraid of an accidental misconfiguration or oscillating amplifier pumping out the full 400kW at low elevation even when the modem was supposedly configured for 20kW or less.
"Can-berra"
... hissss ...
"Come in Can-berra"
... hissss ...
Dum dum dum ...
*_click_* "Apologies Voyager 2. Your call is important to us and will be dealt with as soon as possible in line with normal GP appointment sheduling guidelines. You are currently NUMBER 1 in the queue ...If you wish to hold your call may be answered by a receptionist between 8 and 8.30am next February ... If your circuits have suffered a hiccup, please try rebooting. Returning for a service due to any sort of cough is right out ..."
Australia, the place where the mice are 2m tall and hop on giant legs while keeping their babies in a pouch? Where every spider can kill an elephant with a single bite? Where it is all desert but burns down every summer?Where there are 1000s of kms of perfect beaches but you get eaten by a shark / stabbed by a fish if you set foot in the water?
No that's a totally real place mate, defo .....
They have a strange sort of obesity in Queensland due to the temperature they drink their brown liquid at. Their spare tyres are very high up around the stomach (the organ) just under the rib cage.
The ice cold 'beer' they drink in such quantity chills the stomach so much the body seeks to lay down thermal protection around it. Since evolution has yet to accommodate ice cold liquids vs cold environments this thermal protection is insufficient. But since the stimulus is often ongoing for many years quite thick spare tyres can be seen. You get bandy legged otherwise trim old guys with this weird spare tyre.
You forgot 9 out of the 10 most venomous land snakes in the world. Then there are the sea snakes . . .
There are also the nasty fire ants. I was pleased with my thick high jandals (flip flops) as I passed some on the footpath on my visit to Canberra back in the '80s. I had a nice run up the Black Mountain where they keep the observatory.
I should note that the fire ants were most dangerous wildlife I saw during my visit though one of our party stepped on a snake whilst bathing in Lake Burley-Griffin. Said snake simply swam off. Whilst there we helped persuade a local scientist to relocate to our alma mater in Southern New Zealand. He was the internal examiner of my PhD thesis.
When I first heard the term Deep Space network as a teenager I imagined a set of relay spacecraft strung out along the solar system. When I learned it was just a set of geographically spaced radio telescopes I was somewhat disappointed.
It still seems a rather over grandiose title. The edge of our solar system is hardly deep space in the wider scheme of things.
It's SETI which has tried to do the real Deep Space stuff, not NASA.
We have a transmitter that is working - albeit a bit flakey at the moment - and a spacecraft which by all realistic standards is well beyond its service life but is miraculously still communicating.
We *know* what we need to manufacture and install and the changes we need to make to the transmitter - so why on earth are we risking the spacecraft for *months* uncontrolled when we could build out the transmitter components offline, test them as much as possible, bring them to the site and slap them in with the minimum downtime? Or am I missing something?
This system is an utterly unique resource and losing our ability to control it for months when there are other options seems criminal to me. Yes it has error correction and other systems on board but nothing to what human system engineers can accomplish.
Im seeing far too much of the "Columbia" spirit here - aka "don't worry, it'll be fine"..
Or to quote
"If nothing else works, a total pig- headed unwillingness to look facts in the face will see us through."
Mixed with, to paraphrase
"We're taking an awful risk here, this had better work..."
I just can't see this ending well.
I would hope they had a look at the most likely failure modes and concluded that just about all of them are either unfixable, or can still be fixed after 11 months? It's not like the thing is suddenly going to veer off course and need a human pilot to grab the stick and steady the bird... Even if it were, I don't want to imagine what Battlefield 1942 multiplayer with a ping of 16h feels like.
Let's just hope it's not going to gradually fill the outbox because Earth's mail server is failing to send delivery confirmation...
"Or am I missing something?"
Likely it's a full overhaul, not just transmitter electronics. There's a lot of metal and engineering involved in a dish that size. Maybe rust, maybe new actuators, maybe re-coating the entire dish aqnd a fresh protective coat of paint over the whole structure.
The Register 
Biting the hand that feeds IT
Copyright. All rights reserved © 1998–2024
