BUPO is in no way a computer based on new and advanced technologies. The abbreviation stands for: Unit for the Control of the Mooring and Orientation. But the Mir-complex is no 'ship' that has to be 'docked' at any object, so immediately after knowing the meaning of that abbreviation the word 'mooring' (docking) bothered me. Orientation was no problem at all. But as I indicated in the head of this report it was indeed 'An egg of Columbus' , for BUPO is a very old movement control system which has been used from the first to the last Progress freighter. It was just an analogue control system developed for that what a Progress or a Progress-M had to do: to approach and dock well oriented and flawlessly to space stations like Salyut or Mir.
So BUPO is not a supplement of the for many years existing orientation system on board of Mir, so the Main Computer TsVM-1 of the Salyut-5B type and SUD, the system for movement (or: attitude control). That is system is not 'analogue' but 'digital' and so technologically more advanced than that poor BUPO. But of what avail BUPO would be in the unmanned status of the Mir-space station? In the unmanned status the power consumption has to be reduced to an absolute minimum. This can be achieved by switching off all unnecessary systems. Of course the normal orientation system is far from 'unnecessary', but the power consumption is considerable: the Main Computer itself, but also the gyrodynes, the 12 gyroscopes for a stable control are gluttons. In the unmanned status all control systems are switched off and the station is in the so called 'free drift' with a very modest spin, but so that some solar batteries can deliver enough power to keep the accumulator batteries charged.
But this can go wrong and then the functioning of the normal attitude control by the Main computer, SUD, gyrodynes, etc. to readjust the sun-angle of the solar batteries might be needed. For the power supply as well as for the correct attitude during dockings, for instance a Soyuz with a crew or the unmanned tanker Progress-M1, is compulsory.
But, and this often happened in the past, the attitude control by the main 'digital' system can fail. If a crew would be on board they could adjust the attitude during that 'free drift' with the use of steering rockets and eventually with the VDU, the external X-roll control thruster in the Sofora girder. But when there is no crew, then BUPO can do the job. With commands from earth BUPO can do with the whole complex what her colleagues used to do on board of Progress-ships: control the movements (attitude) by the efficient use of the steering rockets thus preventing a catastrophically uncontrolled situation. The 'digital' attitude control (so with the main computer, gyrodynes, etc.) and the BUPO never can work simultaneously. So it is always 'this or that'. So BUPO is not a supplement of the first system , but an alternative during the absence of a crew in case of failures of the first system.
Regularly TsUP checks Mir's telemetry and if they see that the accumulator batteries do not get enough power from the solar panels TsUP cannot immediately switch on the normal 'heavy calibre' system. To do that more power is needed. In that case BUPO can help using the steering rockets, eventually with the VDU, and correct the attitude so that there will be sufficient power to switch on the main movement control system and to activate the gyrodynes.
Now Progress-M42 is docked to Mir. Progress-M42 cannot do anything with the attitude control of the complex. Progress-M42 has solar panels, but the solar angle of these panels is not enough for a sufficient power supply. So now Progress-M42 gets power from the accu batteries in Mir. If TsUP wants to put Progress-M42 into an autonomous flight, for instance to dump the freighter into the atmosphere, they can undock her and after undocking the solar panels can be put into the right solar angle and pr-M42 can fly autonomously under control of her own BUPO by commands from earth..
The present situation: Both orientation systems are switched off. Still working are the Thermo regulation, the Telemetry and the Radio Command Channels.
There still is that mysterious small air leakage, which is now more mysterious for TsUP is no longer sure that the leakage is in the Kvant-2 module. TsUP is sure that if there will be another mission to Mir (still unsure due to the lack of money), the pressure will be high enough for the crew. It is also possible to add air (oxygen and nitrogen) from tanks (the so called 'ballony') Chris van den Berg, NL-9165/A-UK3202.