Writing this diary is definitely helping me. Is it possible that I am the last human? That when I die, there will be no more human race? No, I can't accept that. There simply must be survivors down below. I fear the only sensible plan will be to jump into the Soyuz and risk landing. It's risky as I have no idea what threat I will be up against when I hit the surface. I will need warm clothes, food and water. Without a recovery team to rendezvous at the landing site, I could have a very long walk back to civilisation. That's assuming there is any civilisation left!

Up here, although I am cut off, I am insulated from events down on the surface. If I get down safely and find that there is simply no-one left, I don't know how I'll react. Logically, it's no worse than being totally alone up here, and at least I won't be facing the oxygen or food running out, but a world without people is almost impossible to imagine.

Loneliness hit me hard today. It's my wife's birthday. I've tried so hard to not think about her, or any of my friends or relatives, but today I toasted her with Russian vodka and then cried all morning. Arth watched me and periodically asked if he should call for medical assistance.

Part of me wants to switch him off, but right now I'm scared of being alone. I need a plan. A target to work towards. Just surviving for as long as I can isn't going to be enough. I need to know what happened down there.

There's a lot of routine stuff to do up here, and it keeps me busy but I can't stop thinking about what could possibly have put MC and the rest of the human race out of action down there. I have to find out what happened.

Started working out a plan to return to the surface. If I live up here until my supplies run out and then make the drop, I'll be going down without supplies. As I don't know what I'm going to find when I get down there, that's clearly not a good plan. I also can't get away from the fact that the longer I leave the return trip, the greater the chance that something will go wrong with the Soyuz before I go. If no-one's going to be sending up a replacement, I can't risk that.

Time to start making preparations.

According to the O2 gas sensor, the farm is producing a measurable amount of oxygen. Letting the plants get a little larger seems to have helped, and I've got stuff growing in all of the available pods. It's difficult to work out how the output compares with the oxygen the station already pumps into the air, but I've told the control system to weaken the oxygen mix by 5% to compensate. I don't feel any different and it means the O2 tanks will last a bit longer. Wish I'd done that a month ago.

Been doing some preliminary calculations; The Soyuz capsule is configured and fuelled to drop three crew-members. With just me on board, I can carry some food and water supplies. It makes sense to carry the equivalent mass of two crew members. Apart from meaning I land with some supplies, it should also ensure the capsule handles like the simulator. It doesn't take much mass variation to drastically vary the handling of the Soyuz.

While I was working how much food I can safely strap into the empty seats, Arth asked me how long I would be gone! He's just a robot, but I didn't have the heart to tell him it's a one-way trip.

About 10 weeks since I had any human contact now. That I can cope with, but what makes it really hard is the lack of evidence of any human activity. The radio is still picking up nothing at all. There are no lights on below. Whatever happened down there has either taken out the entire population or somehow stopped all the light sources and transmitters working. I spent half an hour searching the surface with the telescope again today – nothing. Not one single light! How is that even possible?

Arth helped me load four crates of dehydrated food supplies into the Soyuz. Using duct tape, I think I can safely secure two crates in each of the spare seats. There's not much space in there and crates are less forgiving than people, but I reckon I can still squeeze my suit into the middle position. Water will be the heaviest thing and I need to take enough to rehydrate the food sachets as well as to drink.

There should be no problem taking about a month's supplies with me. If I can't find anything down there, I won't last as long as I can up here, but I can't die up here not knowing what happened down there.

Life is forcing me to make some crazy decisions.

Arth asked if I wanted to play poker. When I said I did not, he asked if I would like to play when I returned from the surface. I still haven't told him that I won't be coming back. He's just a robot, but I still feel sorry for him.

Wrote out an inventory of supplies and equipment I need for my return trip. Obviously, I can't weigh anything so I have to check the main station inventory to get the mass of each item, then add them up as I add them to my inventory. Triple checking everything.

Arth has been helping me transport everything to a large plastic crate I've secured in the transit module. He's been less talkative for the past couple of days. That leaves me wondering why?

Pretty much got the supplies for the trip home sorted now. Fired up the comms system for another scan of all official frequencies. As expected it found nothing. The ham radio came up with nothing either. Whatever's happened down there, there're no transmissions. Looks like my choices are: stay up here and die in a few months' time or descend to the surface and risk dying within minutes or potentially living out the rest of my lifespan.

It's a risk, but I won't find out what went wrong unless I go. I don't want to die without finding out what happened.

Checked over the Soyuz capsule after my exercise session this morning. Doing the checklist on my own is a chore, but everything checked out. The batteries needed charging a little from the station supply but that went without incident. Looks like I need to pick a launch date.

I've explained to Arth about checking the internal hatch is secure. He will maintain many of the station's systems after I'm gone. As long as he has power to recharge from he doesn't need anything else. If the atmospheric processing fails or worse, it won't affect him. While he has power, he'll keep working until some mechanical failure stops him. I almost feel bad about leaving him behind.

I've decided that the best launch date is the last day of this month. There's another crop of tomatoes due to be ready for picking in the next few days. It would be a shame to miss those. I can pick them, pack them and take them with me.

The automatic systems will keep the station in orbit for a few months, maybe a year or so, but then once the orbit has degraded enough to touch the atmosphere, it will fall out of the sky in a matter of a day or two. Without more fuel, there is nothing I can do about that. I hope Arth has shut down before then. He can't feel pain but I don't want him to experience burning up on re-entry.

Started packing supplies into the Soyuz after my morning exercise session. My exercise regime is one place I have had to be strict with myself. No good getting back down to the surface to find my muscles and bones have wasted too much for me to function.

I've done the return trip twice before, but doing it alone will be a new experience, as will piloting it for real. Securing the supplies so they don't pose a danger to me, or move around during the descent, is my biggest issue. There is only one bottle of Russian Vodka left and I plan to take that with me. If I make it to the surface in one piece, I can at least celebrate getting there.

Arth is very keen to help with the loading. He tried to take two bags of food sachets into the Soyuz on his own initiative while I was taking a "break". He got in there fine but had problems manoeuvring to get out again. With the vent tubes and power cables going through the hatchway, Arth could barely squeeze through. After a fair bit of twiddling, I pulled him back out feet first. As long as he doesn't try to turn around inside the capsule, he can actually get in and out unaided, it just takes a while.

Found Arth in the Cupola again this morning, again with the shields open, staring out at the view. I asked him what he was doing and he told me he was looking for signs of people down on the surface. He said he hoped I would not be lonely on the surface. Weird.