Y-Biasing: A New Operational Method for Cassini to Control Thruster Usage while Managing Reaction Wheel Momentum

Brown, Todd S.

doi:10.2514/6.2010-7560

Cited by 14 publications

(3 citation statements)

References 8 publications

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“…On-Earth biases take place while the spacecraft maintains an Earth-pointed attitude. Y biases are designed to reduce the use of the +Z thrusters and were developed in response to the anomalous degradation of some of the +Z thrusters in the RCS A-branch [8].…”

Section: Sources Of Propellant Consumptionmentioning

confidence: 99%

Ensuring Cassini's end-of-mission propellant margins

Sturm

Barber

Roth

2015

2015 IEEE Aerospace Conference

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The Cassini spacecraft is in its final years. On September 15, 2017, Cassini will plunge deep into Saturn's atmosphere never to reemerge; thus concluding its second extended mission and 13 years in orbit around the ringed planet. As of October 2014, the spacecraft is four years in to its sevenyear, second extended mission, the Cassini Solstice Mission (CSM). With three years left and only 2.5% of its loaded bipropellant and 37% of its loaded monopropellant remaining, the Cassini project actively manages the predicted end-ofmission propellant margins to maintain a high confidence in the spacecraft's ability to complete the CSM as designed.Accurate spacecraft navigation, rigorous remaining-propellant estimation, and frequent future propellant consumption prediction have resulted in efficient propellant use and a probability of sufficient propellant margin greater than 99%.

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Section: Sources Of Propellant Consumptionmentioning

confidence: 99%

Ensuring Cassini's end-of-mission propellant margins

Sturm

Barber

Roth

2015

2015 IEEE Aerospace Conference

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“…In order to avoid such a scenario, the Cassini operations team proposed a Y-bias technique which minimizes usage of the Z-thrusters in RWA biases. 2 In Y-biases, the RWA bias occurs by only the Y-thrusters firing. This prevents overburdening the Z-thrusters, and thus increase the life span.…”

Section: Figure 10 Normalized Tank Pressure Coefficient During B-bramentioning

confidence: 99%

“…The Y-bias technique is employed on the spacecraft in order to minimize Z-thruster usage and maximize Ythruster usage. 2 The spacecraft switches to RCS control whenever the RWAs are biased to different speeds. The RCS thrusters remove the internal momentum change in the spacecraft as the RWAs reach their new speeds.…”

Section: Introductionmentioning

confidence: 99%

Cassini Thruster Calibration Algorithm Using Reaction Wheel Biasing Data

Rizvi

2012

AIAA Guidance, Navigation, and Control Conference

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Thrust force estimates for the reaction control thrusters on-board Cassini spacecraft are presented in this paper. Cassini consists of two thruster branches (A and B) each with eight thrusters. The four Z-thrusters control the X and Y-axes, while the four Y-thrusters control the Z-axis. It is important to track the thrust force estimates in order to detect any thruster degradation and for supporting various activities in spacecraft operations (Titan flyby, spacecraft maneuvers). The Euler equation, which describes the rotational motion of the spacecraft during a reaction wheel bias event, is used to develop the algorithm. The thrust estimates are obtained from the pseudo inverse solution using flight telemetry during the bias. Results show that the A-branch Z3A and Z4A thrusters exhibited degraded thrust in November 2008. Due to the degraded thrust performance of Z3A and Z4A, A-branch usage was discontinued and prime branch was swapped to B-branch in March 2009. The thrust estimates from the B-branch do not show any degradation to date. The algorithm is used to trend the B-branch thrust force estimates as the mission continues.

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