Space diary: Days to go until launch

The satellite is being prepared for flight

Just days to go now before the launch of Europe's biggest ever Earth-observation satellite, Envisat, and the dress rehearsal for the countdown is about to begin, as project manager Derek Todman reports in his latest diary for BBC News Online.

Friday 22 February

Today we started at 01:30 in the morning, continuing to remove all the items not required for flight; for example, instrument covers and the large bag that has been covering the solar array.

A number of items were installed this morning required for flight, such as the star sensor baffles, which stop stray light entering the sensor field of view. This would create false star readings and severely degrade the attitude determination measurement.

The solar array is now visible

Once this activity was completed, Arianespace installed the fairing so unless something untoward happens that's the last time most of us will see the satellite.

We do have access to the satellite through a door in the fairing, but more about that later.

The last activity for us today was an electrical check with the fairing on.

Arianespace have started their activities for fuelling the upper stage tomorrow - but we are not involved, so we will have a relaxing day to catch up on some sleep.

Saturday 23 February

The good news today for us is that Intelsat (a communications satellite) was successfully launched last night on an Ariane 4 rocket. That clears the way for us to launch on 28 February (01:07 GMT Friday, 1 March).

Arianespace started filling the upper stage with fuel. This operation is hazardous and therefore satellite access and operations are extremely limited.

The satellite on top of the rocket

The fuel load is approximately three tonnes of hydrazine and six tonnes of nitrogen tetroxide.

These two fuels, when mixed in the combustion chamber, react and provide the thrust to get Envisat into its final orbit once the first stage burn is complete. Today, the hydrazine was loaded and the nitrogen tetroxide will be put on board on Monday.

The personnel that have come in today are either packing or putting the final touches to the procedures for the countdown dress rehearsal, which starts on Sunday night and finishes on Monday.