THE ROLE OF IMPACTS AND MOMENTUM TRANSFER FOR THE EVOLUTION OF ... - AMOS Conference · 2020. 7....

2017 AMOS Technical Conference, 19-22 September, 2017, Maui, Hawaii, USA

THE ROLE OF IMPACTS AND MOMENTUM TRANSFER FOR THE EVOLUTION OF ENVISAT’S ATTITUDE STATE

Thomas Schildknecht, Jiri Silha, Astronomical Institute, University of Bern, Sidlerstr. 5, CH-3012 Bern, Switzerland

Holger Krag Space Debris Office, ESA/ESOC, Germany

ABSTRACT

The currently proposed space debris remediation measures include the active removal of large objects and “just in time” collision avoidance by deviating the objects using, e.g., ground-based lasers. These techniques require precise knowledge of the attitude state and state changes of the target objects. In the former case, e.g. to devise methods to cap-ture the target with a tug spacecraft, in the latter, to precisely propagate the orbits of potential collision partners, as dis-turbing forces like air drag and solar radiation pressure depend on the attitude of the objects.

The long-term evolution of the attitude motion is, among many other causes, depending on the effects of possible im-pacts of debris and meteoroid, while momentum transfer from reaction wheels or other moving internal components may contribute to the root cause of the initial attitude motion. Impacts of small particles like meteoroids and space de-bris pieces on compact space objects are unavoidable events, which were already observed several times, e.g., on Inter-national Space Station, or rather recently on the Sentinel-1A on August 23, 2016.

This paper will discuss a detailed analysis of the effects of momentum transfer from the reaction wheels and of debris and meteoroid impacts for the particular case of Envisat. Based on the physical model of Envisat and the MASTER environment model, the likelihood to have an impact-related attitude rate increase in ten years larger than selected threshold rates was determined.

1. INTRODUCTION

Recently the determination of attitude states, and in particular rotation rates, of space objects became a topic of interest in the space debris community. This is to be seen in the context of the multitude of techniques which are currently pro-posed to remove space debris from orbit or to re-orbit them into disposal orbits. The majority of the techniques to re-move large objects, which are driving the evolution of the space debris population on the long term, require capturing the target with a robotic arm, a net, a harpoon, or another mechanism. The attitude motion is in all these cases a critical parameter and the maximum tolerable target rotation rate is limited.

The attitude motion of an inactive Earth orbiting object may change either due to dissipation of stored internal energy or internal momentum transfer, or because of external forces. Internal energy may be released, e.g., in form of leaking atti-tude control systems or pressurizes tanks, any type of breakup events, and momentum can be transferred from reaction wheels. External torques may results from the interaction with the gravity field gradients and the magnetic field of the Earth or from impulse transfer when colliding with other objects. The aim of this study is to assess the maximum angu-lar momentum change to be expected for the defunct Envisat spacecraft, on one hand due to angular momentum transfer from its reaction wheels, and, on the other hand, from impacts with space debris objects or micrometeorites. The latter was analyzed once for a single impact event and for a statistical particle flux over a then year period. The study was in particular triggered by the sudden acceleration of Envisat’s rotation observed about two months after its failure when Envisat’s attitude changed from an almost stable NADIR fixed attitude to a rotation with 0.547 rpm [1], [2], [3] (inertial rotation period ~ 110s; see Figure 1).

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2017 AMOS

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22 September

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22 September

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2017 AMOS

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22 September

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kg m-2/s) with the wheels to

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spacecraft de

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A

distribution (ri21102014). Thtion in the mas

ON WHEELS

ation of the restem) or alonglong the ̂ axi

in the satellitstem.

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principal axes

[kg.m2]

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termined by E

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of inertia of E

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aded reaction

MMOD parti-covered 10 g - 1 kg.

s is shown inreference sys-action wheels

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m. The maxi-to =

Envisat which

n wheel would

n -s

-=

h

d



Principal axis No.ofreactionwheelsaligned withaxis

Reactionwheel capaci‐ty

[kgm2s‐1]

ENVISAT

momentof

inertia

[kgm2]

Maximum

angularvelocitychange[degs‐1]

Correspondingrotational

period

[hour]

1 40 17023.3 0.1346 0.743

2 40 + 40 124825.7 0.0367 2.723

2 40 + 40 129112.2 0.0355 2.817

Table 3: The maximum angular velocities and corresponding rotational periods of Envisat which can be obtained from reaction wheel(s) assuming different principal axis of inertia.

These results show that a momentum transfer from the reaction wheels cannot explain the observed spin-up of Envisat as the maximum change in angular velocity from this transfer is almost two orders of magnitudes smaller than the ob-served one (period of ~120s).

6. SUMMARY

Effects of debris and meteoroid impacts and of momentum transfer from the reaction wheels for the particular case of Envisat were analyzed. Based on the physical model of Envisat and the MASTER environment model, the likelihood to have an impact-related spin rate change in ten years was determined.

There is an very small probability for a single impact which would result in a substantial change of the angular momen-tum and thus in a substantial change of the spin rate around any axis of Envisat over a ten year time period. A particle of ~100 g is required to spin up Envisat from a stable attitude to about 0.4 rpm, which would be comparable to the angular velocity change observed two months after the contact with the spacecraft has been lost. The probability for such an event is less than 0.25%. Simulations showed that the accumulated momentum transfer from the entire MASTER MMOD population is also minor and would in with worst case assumption result in angular velocity change of 0.04 deg/s.

The maximum momentum which could be transfer from the Envisat’s reaction wheels to its body, assuming that the wheels were fully loaded, would result in an angular velocity change of 0.14 deg/s, 0.037 deg/s, and 0.036 deg/s, re-spectively, for the three main axes of inertia. Again, this is by far not sufficient to explain the observed spin-up of Envi-sat after its failure.

7. ACKNOWLEDGEMENTS

This work was performed in the context of the ESA study “Debris Attitude Motion Measurements and Modelling”, (ESA/ESOC 4000112447/14/D/SR).

8. REFERENCES

[1] Sommer, S., Rosebrock, J., Cerutti-Maori, D., & Leushacke, L. (2017). Temporal analysis of ENVISAT’s rotation-al motion. In 7th European Conference on Space Debris, ESA/ESOC, Darmstadt/Germany, 2017.

[2] D. Kucharski, G. Kirchner, F. Koidl, C. Fan, R. Carman, C. Moore, A. Dmytrotsa, M. Ploner, G. Bianco, M. Medvedskij, A. Makeyev, G. Appleby, M. Suzuki, J. M. Torre, Z. Zhongping, L. Grunwaldt, and Q. Feng, “Atti-tude and spin period of space debris envisat measured by satellite laser ranging,” IEEE T. Geosci. Remote, vol. 52, no. 12, pp. 7651–7657, 2014.

[3] Kirchner, G., Steindorfer, M., Wang, P., Koidl, F., Kucharski, D., Silha, J., Schildknecht, T., Krag, H. & Flohrer, T. Determination of Attitude and Attitude Motion of Space Debris, Using Laser Ranging and Single-Photon Light Curve Data. In 7th European Conference on Space Debris, ESA/ESOC, Darmstadt/Germany, 2017.

[4] Flegel, S., Gelhaus, J., Möckel, M., Wiedemann, C., Kempf, D., Krag, H. and Vörsmann, P. Maintenance of the



ESA MASTER Model – Final Report. Technical Report ESA Contract Number: 21705/08/D/HK, Institute of Aero-space Systems (ILR), June 2011.

[5] Bargellini, P.; Garcia Matatoros, M. A.; Ventimiglia, L.; Suen, D., Envisat Attitude and Orbit Control In-Orbit Per-formance: AN Operational View, 6th International ESA Conference on Guidance, Navigation and Control Systems, held 17-20 October 2005 in Loutraki, Greece. Edited by D. Danesy. ESA SP-606. European Space Agency, 2006. Published on CDROM., id.52.1


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