TRACKING OF PHOBOS-GRUNT MISSION IN LOW EARTH ORBIT

Alexander S. Samotokhin, Andrey G. Tuchin M.V. Keldysh Institute of Applied Mathematics of Russian Academy of Sciences,

Moscow, Russia

Sergey A. Sukhanov, Zakhary N. Khutorovsky, Andrey V. Rykin Interstate Joint-Stock Corporation “Vympel”, Moscow, Russia

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On-Earth control structure of Phobos-Grunt mission

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The schedule of LEO operations

Operation Time, Msk Note

Launch to base orbit 00:16:03.1 - 00:18:28.7 Separation of spacecraft from 2nd stage of the rocket

Base orbit 00:18:28.7 - 02:55:47.9 Hp=207 km

Ha=347 km

1st maneuver 02:55:47.9 - 03:05:18.2 V=815.7 m/s

Separation of external tank

Intermediate orbit 03:05:18.2 - 05:02:48.8 Hp=244 km

Ha=4162 km

2nd maneuver 05:02:48.8 - 05:20:09.9 V=2851.9 m/s

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The trace of Phobos-Grunt in low Earth orbits

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Relative movement of PG and 37947 (SGP4 model)

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Relative movement of PG and 37947 (SGP4 model, compensation of time error is applied)

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The evolution of A/m ratio (Nov 9 – Dec 10)

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Analyzed orbital parameters

The draconic period (the time that elapses between two passages of the object through its ascending node)

The height of perigee

The latitude of under-satellite point in perigee 

Considered parameters are not osculated elements. These parameters were calculated during one revolution with use of the corresponding propagator.

The designations used in subsequent figures

The propagated evolution

Actual Russian SSS data

Actual American SSS public data (TLE)

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Evolution of the orbit parameters Nov 9-22passive movement, A/m=0.0016 m2/kg (nominal)

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Evolution of the orbit parameters Nov 9-Dec 6passive movement, A/m=0.0016 m2/kg (nominal)

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Evolution of the orbit parameters Nov 9-22passive movement, A/m=0.00093 m2/kg (58% nominal)

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Evolution of the orbit parameters Nov 9-22nominal A/m, acceleration along velocity: 2.83∙10-6 m/sec2

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Evolution of the orbit parameters Nov 9-22accelerations: along velocity: 2.49∙10-6 m/sec2, s/c-Sun direction 1.16∙10-5 m/sec2

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Conclusions

1. Really space surveillance systems were the only source of information about behavior of Phobos-Grunt onboard systems in low Earth orbit. It is a very unusual situation.

2. The data both Russian and American SSS proves that the movement of Phobos-Grunt were not passive during the first 12-13 days after the launch. These data allowed to obtain a estimation of actual perturbations.

3. The interaction between on-Earth control structure of the mission and Space surveillance system was unsatisfactory. It is necessary to provide real time data exchange between these systems in the future.