The telescope itself is mainly an infrared telescope; the location ensures that the cryostat can be kept as close to absolute zero as is humanly possible. 0.1 microkelvin was the goal, though in practice it was usually a shade north of that. Typical operating temperature for the cryostat was 0.117 uK, and that was well within the tolerance of 0.14 uK, above which the instrument lost about a third of its sensitivity to the very faint and distant sources it was built to observe. On my watch it had peaked at 0.135 uK, which happened after a helium chiller had gone out and the superfluid helium bath went viscous.
Being far out at the edge of the solar system wasn't enough; there was an elaborate three-stage sun shade protecting the telescope from solar radiation--even at 30 AU from the sun that was not trivial--and there further were other shields protecting the telescope from the heat emitted by its own radiators and chilling systems. The telescope was often referred to as "the coldest place in the solar system" but in fact it was the coldest place within a light year of the sun.
The maintenance station shared the same orbit as the telescope, twenty kilometers away. There was another heat shield between the station and the telescope, of course. In the event of a malfunction, it was my job to direct repairs.
"Direct", I said, not "effect". The heat given off by a man in a space suit would overwhelm the cryostat chiller and render the entire instrument unusable for days while it cooled off again; I couldn't go anywhere near the thing except in the most dire of emergencies. I had robots, waldoes, and telepresence gear for making repairs.
Being so far out, mail service is spotty. I got the occasional message, of course, from friends or relatives, but it takes light four hours to get from Pluto to Earth, and an equal time to get back; conversations are impossible. And because the habitat had to be small--to keep heat pollution under control--I was the only person there. It was, as I said, lonely.
Typical duty cycle for the telescope is a year. It pays well. And it's not cold--the station exists in a vacuum, and it's no problem to keep it toasty warm--but for all of that it felt like being stationed in Siberia must have, a century or so ago.
For most of the year I hadn't really noticed the isolation. I had my own research to work on (I could sneak glimpses through the telescope during gaps in its observation schedule) and I'm one of those people who can get along just fine with a computer, the right software, and my library of books and videos. But the holidays came around, and that's when I started to long for company.
It started, simply enough, with my sister sending photos of the kids dressed up for Halloween. Then came Mom and Dad, with a video shot at Thanksgiving; and the well wishes for Christmas had started coming in shortly thereafter.
The rules allowed for holiday decorations, but I hadn't seen the point of it--if I'd brought any with me it would have counted against my weight allowance, and putting up decorations meant I'd just have to take them all down again. So as Christmas came into near view, it was just like any other week. I found myself regretting not bringing, at least, a string of lights, but it was too late now, and the next supply ship wouldn't come before February.
I'd said there were robots--there are, at the telescope itself, kept at extreme low temperature and built only to operate at that end of the thermometer; but there were a few maintenance robots in the station, too, there to help out in case of emergencies and with routine maintenance. They'd been labeled A, B, and C, but of course over the five years the telescope had been in operation, the various caretakers had given them names, such that now they were named Abernathy, Balbo, and Cron.
A, B, and C were the closest thing the caretaker had to company. Each had a personality, carefully built by cybernetic psychologists, and though they were supposed to be wiped clean at the end of a caretaker's cycle, they never had been. Seems the caretakers get attached to them, and can't brain-wipe a friend. I'd thought that was silly. I mean, they're just robots, right?
It was Abernathy who spoke up first, that day. "Boss, I've noticed that you're moping." He was usually direct like that.
"Yeah, you. Right now, for example: you have only consumed sixty percent of your breakfast."
I looked at the plate in front of me. "I'm just not hungry."
Balbo, who had prepared the meal for me, said, "I have prepared that to your specifications, and when I check with Cron he tells me that this morning's urinalysis shows your blood sugar was at 67 micrograms per deciliter. You should be hungry, boss."
I looked at the two. Before I could say anything, Abernathy spoke up. "Our observation of our various bosses over the years has demonstrated that, around this time of year, some bosses get lonely. Is there anything we can do, boss?"
I said, "Don't worry about it. You guys know humans are social creatures."
"Holidays are the hardest times for you," Abernathy agreed. "But our job isn't just to maintain the station; as you know we also must care for the caretaker."
Balbo added, "Which means you should finish your meal."
Sighing, I finished the food, then handed the plate and fork to Balbo. "Any maintenance scheduled today?" I asked Abernathy.
"Not today, boss. It's Christmas Eve, so none scheduled tomorrow, either." There was a pause while he consulted the station's computer. "Cryostat shows as operating within nominal limits. There will be an observation pause from 14:32 through 15:55; shall I aim the telescope at Betelgeuse during that time and continue your observations?"
"Please." Betelgeuse had been acting funny for the better part of sixty years; some folks thought that meant it would be exploding soon. I was trying to characterize the luminosity curve in an attempt to predict how it would explode. In theory the telescope was supposed to be in use 24/7 but in practice there were always gaps in the program, which is why there was no shortage of grad students to take maintenance duty out here.
Sighing, I went to the exercise room and did cardio for the mandated twenty minutes, then had a shower. If there was no work scheduled today--and tomorrow!--what was I going to do? Mope for forty-eight hours?
I was about to take a nap when an alarm hooted. Cron was nearest to me; he said, "Boss, the telescope is reporting a cryostat overheat."
"Got it, on my way," I said, and hurried to the command center.
The command center is a round pod stuck to the side of the station. Its entire inside surface is one big display screen, and there are two circular consoles, one at the usual height and one overhead, from which the teleoperating arms--waldoes--depended. The caretaker sat in a typical office chair and did whatever he had to in order to maintain or repair the telescope.
As I sat down I was already scanning the floor console for the diagnostic codes. The computer wanted to send a maintenance bot from the storage shed to the cryostat, and I allowed that; then I dug deeper into the problem while the bot was en route. What I saw made no sense: the cryostat was colder than normal, about 0.089 uK, but the image sensor was reporting a sensitivity fail, which the computer had interpreted to mean it had overheated.
"Computer, let me see the cryostat," I said. Immediately the cameras inside the cryostat chamber went on, and all I could see was grey fog. Switching cameras didn't help, either. "Camera diagnostics."
"Cameras functioning normally."
Great. It was really there. Well, there was only one possible source for grey fog in the cryostat chamber. "Computer, check coolant pressures."
"Primary, nominal. Secondary, nominal. Tertiary, fail, low."
"Shut down coolant pumps on circuit three."
With that, the fog almost immediately began to disperse, which confirmed my fears: one of the cooling circuits had sprung a leak. It explained why the cryostat was cooler than normal--sublimating superfluid helium carried away heat--and it also explained the fog. This was going to take a long time.
"Watch what you wish for," I grumped.
"Directive not understood," the computer replied.
The repair bot was on station, so I switched over to telepresence mode and got to work. Repairing a helium leak, by remote control, is a finicky process, so I didn't bother: I just replaced the manifold, a slow, exacting process. The robot couldn't do it; I had to use waldoes and do the job myself.
As I worked on removing the faulty manifold, I became aware of noise behind me. It was periodic noise, and it only seemed to occur when I was trying to do something precise. The sixth or seventh time it happened, I snapped, "What in blue blazes is going on out there?"
Abernathy replied, "My apologies, boss. We're attending to maintenance functions."
"Keep it down, damn it! I'm trying to work, here! It's hard enough to do this shit without you guys having a friggin' rumble out there."
"We do apologize, boss."
"What a way to spend Christmas Eve," I grumped, seizing the waldo and resuming the work. Disconnecting the coolant lines was really difficult, even with the best telepresence software and hardware the robotics industry had to offer. I could feel everything the waldo touched as if I were touching it with my bare hand--well, with temperatures suitably adjusted, since actually touching something that cold would give you severe frostbite in a matter of seconds--but it was a tight space, and the parts were tiny.
Finally, though, the leaking manifold was floating free. The robot obligingly grabbed it while I leaned back and took a break. I sighed, wiping sweat off my forehead.
"What the hell was that?" I demanded.
Cron stuck his head into the command center. "Apologies, boss! Abernathy and Balbo collided."
"Am I going to have to fix you guys next?"
"No, boss. Momentary operational error. It won't happen again."
"It better not. The last thing I need right now is for you guys to go out of commission. What's the cryostat temperature?"
"0.112 microkelvin, boss." Cron paused. "That's with the primary and secondary cooling circuits running at 118% of capacity. With the repair bot in the cryostat chamber, in an hour they'll have to run at 125% of capacity to maintain temperature within limits. As you know, that is emergency maximum speed. Overheat will occur eight to ten minutes after that speed is reached."
I consulted the clock. It had taken me almost ninety minutes to get the busted manifold out. This didn't look good. If the cryostat overheated, it would take hours to cool it down again; and if it overheated badly enough the telescope would shut down. That would take days to fix.
Well, nothing for it. I commanded the repair bot to get the new manifold in place, and I'd set to reconnecting it as soon as it was. Meanwhile--
"Hey, Balbo! Get me a sandwich and something to drink," I yelled.
I wasn't paying much attention to the robot, but was watching the screens; when Balbo handed me the sandwich, though, I noticed then. My gaze actually traveled from the robot's hand, up its arm, to its central body.
"What on Earth--" I demanded, looking at the glittery particles clinging to the robot's exterior. They were bits of foil-covered mylar, the kind of thing they made survival blankets from, but also used for the vacuum preservation of food.
"Apologies, boss," the robot said. "I had some trouble with the packaging of the rations."
"None of that got in my food, did it?"
"Make sure you clean yourself up. I don't want any of that getting anywhere else."
"Of course, boss."
I wolfed down the sandwich, not paying any attention to what it was. It could have been steamed cardboard for all I noticed; I was too busy watching the robot on the monitor getting the cooling manifold in place. By the time I got the food eaten and had swigged down the drink, the manifold was ready, so I began the finicky work of reattaching it and fastening it in place.
It took concentration; it was always easier to disassemble than to reassemble. Whatever noises the robots had been making in the station had largely subsided, so I was able to concentrate fully now. The work was exacting and I had to get it done as quickly as possible; at one point Cron stuck his head into the command center and told me that the coolant pumps were now running at 125% of capacity and I told him to get the hell out and not bother me.
But eventually the job was finished, and the leak test showed that the tertiary cooling circuit was tight again; I commanded the robot to return itself to the stable and put the waldo arms into their standby positions, then sagged into the seat, sweating profusely. The diagnostic telltales were winking from red to yellow to green, and as I watched the last of them went green.
According to the log, the cryostat temperature had risen to 0.135 uK with one cooling circuit out and the other two at 125% of rated capacity, leaving my record intact. That was fine by me. And but for the few minutes while the cryostat chamber was filled with helium fog, observation had continued, unimpeded.
I got out of the seat, kinks in every muscle. Sighing, I staggered off to the hab module and had a very long, hot shower, the last half set on "massage". Once out and dressed in clean clothes I felt like I was made of rubber, and hoped there would be a moratorium on further emergencies until after tomorrow.
Cron met me in the corridor on my way to my cabin. "Boss, there's something you need to see in the common room."
I sighed. "Cron, I'm exhausted. Is it an emergency?"
"Then it can wait until tomorrow, can't it?"
"You need to see this, boss."
"Damn it, Cron, I'm not in the mood for games! Tell me, what is it?"
"It'll only take a few minutes, boss."
Robots are not supposed to be able to ignore a direct order like that, but fatigue had dulled my senses and I didn't notice it. Besides, although none of the robots was even remotely android, nor capable of expression, somehow Cron gave the impression of being--well, not nervous, but anticipating something.
"Fine," I snapped, and turned towards the common room. A few frustrated steps later I stopped at the entry to the common room and gaped at the sight.
There was a Christmas tree on the table. From the door it looked almost real.
Closer inspection showed it was not, of course. Copper wire had been twisted, with shreds of green mylar entangled to resemble foliage, and the whole thing had been connected together to make a pretty decent simulacrum of a small fir tree. An LED lighting strip had been disassembled and the LEDs strung together with fine wire to make a perfectly acceptable string of lights; ordinary objects had been repurposed into ornaments, and silvery mylar tinsel completed it. There was even a star on top, foil covered plastic or cardboard, with a tiny LED at each of the five points.
I looked at the robots. "Wha--?"
"Merry Christmas, sir," they chorused, and then started singing "Silent Night" like a barbershop quartet. I don't know which one of them did two voices, but they pulled it off handily.
After that, I understood completely why no one had ever memory-wiped these robots.