MAGION-5 is on the exhibition in Prague, January 1996.

MAGION-5 S/C was launched into the orbit as a part of INTERBALL-2 S/C on August 29, 1996. When the main S/C solar orientation was developed the subsatellite was separated and after this the subsatellite was controlled by the Czech colleagues (the Institute of the Atmosphere Physics of the Czech Academy of Sciences, Panska Ves station, Czech Republic). The communication link with the MAGION-5 subsatellite was interrupted on August 30, 1996 and it was not restored later.

Below you will find a short abstract from the report prepared by the Czech and Russian colleagues on the analysis of the MAGION-5 S/C loss reasons.

According to the technical requirements of the INTERBALL mission both the main S/c and the subsatellite are solar oriented and they should fly at a small distance from each other. Therefore the subsatellite separation is posibble only when the main S/C is in the given orbit and when its solar orientation and the selfchecking are performed. So, the subsatellite is in the absolute shadow for several hours and is being intensively cooled. Not to be cooled so quickly, the heaters supplying by the current from the main S/C via a cable are switched on. After the subsatellite separation this cable is cut first, and then the command to switch on the separating cooling system is sent.

08.22 Moscow time, - INTERBALL-2 S/C launch.

10.15 Moscow time - the first telemetry data from the temperature sensors : -8 deg.C on the MAGION-5 S/C chemical battery.

10.29 Moscow time - the subsatellite heaters are switched on.

12.12 Moscow time - the transmitter-beacon of the main S/C is switched on and its reception from Panska Ves is confirmed.

12.38 Moscow time - after sending the command of pyroknives operation and the confirmation of this command there was sent a command to separate the subsatellite with the rated speed of the primary distance between spacecraft of 0.2 m/s.

The subsatellite, for the moment of the separation, had the temperature of the chemical battery +9deg.C by the telemetry data from the main S/C.

Then the following events took place.

When the command for the subsatellite separation was sent, the action of the mechanical contact sensors was not fixed. This sensors were installed onboard the main S/C to determine the fact of separation. The Russian side, in the working order, applied with the request to Panska Ves to check out the fact of the subsatellite separation by subsatellite own mechanical contact sensors.

At this time the Panska Ves station fixed the signal of the MAGION-5 on-duty transmitter that pointed to the fact that its contact sensors had acted and the automatic deployment cyclogram had begun. However, the signal of the MAGION duty transmitter turned out to be too weak for data decodering, and so, some time was lost to switch on a duty service telemetry via the other transmitter. The data received at the end of this session showed that the subsatellite command system operated, on-board voltage from the buffer chemical batteries charged on the Earth supplied the service systems, but there were no current of the solar panels, and, consequently, no recharge current of the on-board batteries, and the temperature inside the subsatellite was falling down.

In accordance with the information from the Russian side and due to some design peculiarities of the separation unit, unfortunately the following conclusion appeared: the MAGION went away from the mounting place for 1 - 5 mm, but it remained in the main S/C composition on its shadow side, that was why , as it seemed at that time, there were no solar panels current, the temperature was decreasing and the signal of the duty transmitter was weak because it was shielded by the main S/C.

The Panska Ves station proposed that the MAGION was not separated and automaticaly the commands to block the deployment of all the booms and S/C solar panels were sent (as it then turned out, that was a fatal decision as, during that time, the chemical batteries capacity was consumed and the time to recognize the situation over was lost). The complete TM system was not managed to be switched on as the temperature inside the MAGION-5 was less than -20 deg.C. That was the end of the first communication session.

At the beginning of the radio visibility of the second revolution the command to switch on the STS digital TM was sent and it worked normally.

The transmission rate was 40, 20, 5 kbit/sec.

The following systems were checked:

- receivers and command decoders in the range of 149 MHz;

- TM transmitters in the ranges of 137 and 400 Mhz;

- switching system of modulation filters and separate transmitter modulators;

- system of secondary power converters for supplying the on-board systems ;

- SMT small (on duty house keeping )TM system ;

- STS digital TM system ;

- solar sensors system;

- house-keeping measurements unit.

There was performed the switching on of the KDU (gas jet reactive installation with cold gas) system and of the following scientific instruments : SAS, KEM (to check the analog modulation of the sensors), videocamera VIM (to check the separation moment: the instrument showed the presence of an object near the lens (the lens focal distance did not make it possible to view this object in details) that was interpreted as a proof of non separation, but later it turned out that it was a non-deployed antenna of the subsatellite); SG-R8 magnitometer, that for a long time operated as a rotation rate and orientation sensor of the subsatellite in the magnetic field.

At 18:32 Moscow time after the agreement with the Russian Flight Control Center a command was sent to switch on a twist nozzle of the KDU (1 pulse for 16 sec.) to check the availability of a rigid connection between the S/C. As a result of a performed manoeuvre, the period of the twisting of the main S/C was not changed (with the accuracy of up to 5 symbols), and the period of the subsatellite rotation after the twisting decreased for 16.5 sec. This met the requirements of a normal operation of the KDU system under the conditions of a complete separation of the main S/C and the subsatellite.

The data of the KEM instrument (Russia, Czech) obtained from the MAGION-5 S/C.

For this fact and taking into consideration that the solar sensors showed normal Sun and the tendency of the distribution of subsattelite temperatures was approaching a normal one, there was drawn a conclusion that the subsatellite had separated and that there existed an abnormal on-board situation with the power supply system and due to that, there was no current in the solar panels. Unfortunately, by this time, almost all accumulator energy reserve was used and after the command for a complete deployment, that still passed, was sent it became clear that there would be no current from the solar panels, the power was at the limit most likely due to the failure of a primary converter (as it has been assumed before) and in addition the radiovisibility came to its end.

The session was short by the radiovisibility conditions during which there were sent the commands to switch off the power comsuming systems of the subsatellite.

The data of the SGR magnetometer (Rumania). The arrow showed the time of switching of the propulsion installation for the MAGION spinning intended for estimation the degree of the connection between two vehicles.

On 30.08.96 in the 4th revolution starting from 03:25 the commands to switch on to a spare converter, connected with its separate power panels started to be sent. Because of the power supply insufficiency this command passed only half an hour later. At 03:57:38 there was at last a charge current registered that was higher than the discharge current; immediately the command to switch off TM transmitters and other power consuming systems was sent to maximum charge the batteries, but there occurred no registration of the commands passing because of the loss of the communication with the subsatellite due to the decrease of the on-board voltage lower than the minimum admissible level (to have longer possibility to work with the subsatellite the Czech experts switched off the recharging protection system ).

Note: While analyzing the subsatellite control it should be noted that the minimum current consumed by the subsatellite systems is 200 mA, and in the best case, if there is no recharging current of chemical batteries , their energy reserve should have been consumed in a day (especially as by the moment of separation the chemical battery has already lost 28 of the primary capacity partly due to a natural self-charging for those 7 days that passed from the moment of subsatellite mounting and partly due to a low temperature). This made the Czech experts begin switching on of the main subsatellite systems to detect the instruments' condition paying no attention to quicker discharge of the chemical batteries in this case.

The MAGION-5 subsatellite did not respond.

Thermal Mode

Taking into accound the data from the MAGION-5 thermal sensors there was performed the temperature field approximation by the moment of the subsatellite separation. It showed the approximate correspondance of approximated temperatures with their expected values with the correction to a natural inaccuracy of the temperature values and the number of the points under processing.One can surely state that starting from the separation moment the subsatellite body temperatures increased due to a solar irradiation heating, and the chemical battery temperature decreased due to a heat exchange with a massive, as compared with the battery itself, cooled S/C body. Thus, the main operation with the accumulator battery was performed under low temperature values but taking into account the velocity of the natural reduction of the power reserve that was a right decision.

Power Supply System

As a result of the stage by stage simulation of the situation with the power supply system performed at the Institute of the Atmosphere Physics of the Czech Acacdemy of Sciences there was rejected earlier version of the non-standard operation of the primary converter and there was drawn a conclusion that the reason of the non-standard aboard operation of the subsatellite power supply system was a short circuit between current carrying wires of the second and the third elements of solar panel N3 and the "ground" after the subsatellite assembly aboard the main S/C that could be the consequence of the mechanical damage of the solar panel.

Chemical Battery

Due to the processing of the full array of the telemetry data obtained from the MAGION-5 S/C the conclusion was drawn that the decrease of the reserve of the chemical batteries occured in a full correspondence with their load. The subsatellite batteries operated according to the standard.

Spare Primary Converter

A spare onboard set of the primary converter with its solar panels operated normally and could provide up to 1/3 of the required power and provide the operation of the subsatellite in the orbit in the composition of the satellite-subsatellite by the short scientific program in the mode of the interchange of the periods of the chemical batteries recharging and the operation of the scientific equipment set.

Repeated Initialization of the Subsatellite

As there was a probability to improve the characteristics of the power supply system due to the heating of the subsatellite in the shadow-free orbit, the Czech experts developed a program of the repeated initialization of the subsatellite. Its essence was in the continuous transmission of a set of commands to the board switching off all power-consuming systems of the subsatellite and setting the chemical batteries to the mode of the direct recharging from the solar panesl. The works were done within the period from October 29 to November 11, 1996. The set of commands was sent in all three frequencies of the ranges of the command radioline (in the range of 149 MHz - two frequencies and 450 Mhz). But inspite of all the attempts the signal from subsatellite wasn't registred.

The reasons of loosing the MAGION-5 subsatellite during the second day after the launch were:

• short circuit in the circuit of one of solar panes (possibly because of the mechanical damages after the last ground test while connecting the subsatellite with the separation unit) that made it impossible to charge the batteries from the main set of primary converters;

• the errors in the action of the control group caused by the report of the Russian side about the absence of the signal of the subsatellite separation system limit switches from the side of the main vehicle that did not allow to control group to estimate the situation in time and to turn to the supply of the subsatellite from the spare primary converter.

The subsatellite operation in the non-standard mode showed, in principal, high possibilities in switching the duplicating life systems and in providing the possibility to obtain the full information from it and to control it in the emergency mode. However, these possibilities were not correctly used.

For the accident reason the subsatellite should have played its role approximately by 1/3 of the power supply (later on due to the manoeuvre there would have been possible to repair the short circuit in the solar panels). However, the mistaken interpretation of the information sent from various sides in the first two revolutions did not make possible to do it.

It is evident that in future for such launches there will be sensible to test both standard and non-standard separation of spacecraft, expecially if they are controlled from different ground stations of different countries. At present there has been modified (changed) the concept of the onboard system of the self-diagnostics of the status of the support systems and scientific instruments making it possible to inform the control group on the damage aboard the S/C and to switch automatically the microsatellite systems to more favourable mode.

Subsatellite project scientist from Czech side P.Triska ptr@ufa.cas.cz
Subsatellite technical manager from Czech side J.Vojta jvo@ufa.cas.cz
Institute of Atmospheric Physics, Czech Acad. Sci., Prague, Czech Republic.