Cage Instability of XMM-Newton's Reaction Wheels Discovered during the Development of an Early Degradation Warning System

Kirsch, Marcus; Esoc, Esa; Martin, Jim; Pantaleoni, Mauro; Southworth, Richard; Webert, Detlef; Weissmann, Uwe

doi:10.2514/6.2012-1275204

Cited by 11 publications

(7 citation statements)

References 1 publication

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“…Dry bearing cage instability anomalies with symptoms very similar to those described earlier have also been observed in two (of four) attitude control reaction wheels of the ESA mission XMMNewton [16,17]. The XMM-Newton observatory was launched in 1999 for a 10 year mission.…”

Section: Cassini Rwa Bearing Cage Instabilitymentioning

confidence: 59%

In-Flight Performance of Cassini Reaction Wheel Bearing Drag in 1997–2013

Lee

Wang

2015

Journal of Spacecraft and Rockets

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As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four year prime mission (2004)(2005)(2006)(2007)(2008) and has since been approved for a first and second extended mission through September 2017. Cassini uses reaction wheels to achieve the spacecraft pointing stability that is needed during imaging operations of several science instruments. The Cassini flight software makes in-flight estimates of reaction wheel bearing drag torque and made them available to the mission operations team. In trending these telemetry data (for the purpose of monitoring the long-term health of the reaction wheel bearings), anomalous drag torque signatures have been observed over the past 15 years. One of these anomalous drag conditions is bearing cage instability that appeared (and disappeared) spontaneously and unpredictably. Cage instability is an uncontrolled vibratory motion of the bearing cage that can produce high-impact forces internal to the bearing, which will cause intermittent and erratic torque transients. Characteristics of the observed cage instabilities and other drag torque "spikes" are described in this paper. In day-to-day operations, the reaction wheels' rates must be neither too high nor too low. To protect against operating the wheels in any undesirable conditions (such as prolonged low spin rate operations), a ground software tool named a reaction wheel bias optimization tool was developed for the management of the wheels. Flight experience on the use of this ground software tool, as well as other lessons learned on the management of Cassini reaction wheels, is given in this paper.Nomenclatures c = viscous coefficient of wheel bearing lubrication system, N · m · s∕rad Gω = function of wheel spin rate ω defined in Eq. (5) I RWA = moment of inertia of reaction wheel rotor, kg · m 2 K I = integrator gain of reaction wheel assembly drag torque estimator, kg · m 2 ∕s 2 K P = proportional gain of reaction wheel assembly drag torque estimator, kg · m 2 ∕s L −1 = inverse Laplace operator s = Laplace variable, rad∕s T D = Dahl drag torque of reaction wheel bearing system, N · m T Drag = total drag torque of reaction wheel bearing system, N · m ξ D = damping ratio of reaction wheel assembly drag torque estimator τ = time constant of wheel speed decay [see Eq. (4)], s Ω 0 = initial wheel spin rate of coast-down test, rad∕s ω = angular rate of the reaction wheel, rad∕s ω D = bandwidth of the reaction wheel assembly drag torque estimator, rad∕s

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Section: Cassini Rwa Bearing Cage Instabilitymentioning

confidence: 59%

In-Flight Performance of Cassini Reaction Wheel Bearing Drag in 1997–2013

Lee

Wang

2015

Journal of Spacecraft and Rockets

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“…During intervals of stable pointing, when it is expected to change only slowly, the current drawn by RW1 showed sudden jumps to higher values, remained there for some seconds to minutes before returning to its nominal value. The reason for these sudden jumps is almost certainly a sudden increase in the friction of the reaction wheel bearings, the so-called "cage instability" [see ref 8 ]. RW1 has been turned-off and is awaiting re-lubrication -each reaction wheel has an oil reservoir that allows oil to be injected into the bearing in order to cure the caging problem.…”

Section: Spacecraft Statusmentioning

confidence: 99%

XMM-Newton operations beyond the design lifetime

et al. 2012

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After more than twelve years in orbit and two years beyond the design lifetime, XMM-Newton continues its near faultless operations providing the worldwide astronomical community with an unprecedented combination of imaging and spectroscopic X-ray capabilities together with simultaneous optical and ultra-violet monitoring. The interest from the scientific community in observing with XMM-Newton remains extremely high with the last annual Announcement of Observing Opportunity (AO-11) attracting proposals requesting 6.7 times more observing time than was available. Following recovery from a communications problem in 2008, all elements of the mission are stable and largely trouble free. The operational lifetime if currently limited by the amount of available hydrazine fuel. XMM-Newton normally uses reaction wheels for attitude control and fuel is only used when offsetting reaction wheel speed away from limiting values and for emergency Sun acquisition following an anomaly. Currently, the hydrazine is predicted to last until around 2020. However, ESA is investigating the possibility of making changes to the operations concept and the onboard software that would enable lower fuel consumption. This could allow operations to well beyond 2026.

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“…During the development of the XMM-Newton Early Warning System (XEWS) 9 , that is intended to detect early degradation of sub-systems in order to be able to start counter actions, we spotted a strange behaviour of one of our four reaction wheels. First thinking of a S/W feature in our system it turned out in fact it was bearing noise that had not been flagged by the standard out-of-limit system of the Mission Control System.…”

Section: B Discovery and Mitigation On Xmm-newtonmentioning

confidence: 99%

Extending the lifetime of ESA's X-ray observatory XMM-Newton

Kirsch¹,

Elfving²,

Kresken³

et al. 2014

SpaceOps 2014 Conference

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ESA's XMM-Newton space observatory launched in 1999, is the flagship of European Xray astronomy and the most powerful X-ray telescope ever placed in orbit. The mission, originally designed for a 10 years lifetime, is planned to be operated long into this decade since spacecraft and instruments are performing admirably without major degradation. The ultimate mission end of life was defined as 2019, limited by the hydrazine reserves on board. Since scientific demand on XMM-Newton is very high and the mission has been ranked top level by the ESA advisory structure, various options to reduce the fuel consumption have been investigated. Some of these have been put in place in the course of the last years, especially we have updated the on-board software of the Attitude Control Computer to allow operating all four reaction wheels in parallel instead of only running three of them as done previously. Simulations and experience from ESA's HERSCHEL mission have shown that this should reduce the fuel consumption by up to a factor of two. In addition, operating with four reaction wheels offers the possibility to apply some measures against increased bearing noise due to aging, which has been detected on two of the XMM-Newton reaction wheels. The usage of all fuel saving methods may extend the potential lifetime to 2030. We present the implementation and results of the applied fuel saving methods and describe the increased bearing noise and its mitigation measures. In addition will report on the outcome of relubrication exercises performed on two of the wheels to cure the increased bearing noise. Furthermore we describe plans that are currently developed to operate the Hydrazine Propulsion System in the so-called near fuel depletion regime at the end of the technical life limit. In addition, ground segment evolution related to hardware, software and automation possibilities facing the new very long term perspective are discribed.

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Cage Instability of XMM-Newton's Reaction Wheels Discovered during the Development of an Early Degradation Warning System

Cited by 11 publications

References 1 publication

In-Flight Performance of Cassini Reaction Wheel Bearing Drag in 1997–2013

In-Flight Performance of Cassini Reaction Wheel Bearing Drag in 1997–2013

XMM-Newton operations beyond the design lifetime

Extending the lifetime of ESA's X-ray observatory XMM-Newton

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