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NGGM ASSESSMENT STUDY Progress Meeting 3 TAS-I, Torino, 26 May 2010

NGGM ASSESSMENT STUDY Progress Meeting 3 TAS-I, Torino, 26 May 2010. WP 2121 Measurement Technologies (ONERA). Input for accelerometer technology review (1/1). ACC2. ACC3. ACC1. ACC4. Concept 3. Linear acceleration. Cross-track axis Y Radial axis Z. Sat-Sat axis, X.

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NGGM ASSESSMENT STUDY Progress Meeting 3 TAS-I, Torino, 26 May 2010

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  1. NGGM ASSESSMENT STUDYProgress Meeting 3TAS-I, Torino, 26 May 2010

  2. WP 2121 Measurement Technologies (ONERA)

  3. Input for accelerometer technology review (1/1) ACC2 ACC3 ACC1 ACC4 Concept 3 Linear acceleration Cross-track axis Y Radial axis Z Sat-Sat axis, X Scale factor stability Sat-Sat axis, X Cross-track axis Y Radial axis Z Linear acceleration bias Bias along Y < 210-7 m/s2 Bias along Z < 210-7 m/s2

  4. Input for accelerometer technology review (2/2) ACC2 ACC3 ACC1 ACC4 Angular acceleration • Angular acceleration around X: • from aZ1 – aZ3 et aY2 – aY4, • Angular acceleration around Y: • from aX2 – aX4 , • Angular acceleration around Z: • from aX1 – aX3

  5. Proposed concept of accelerometer X Z Y g • Short-term solution with TRL 9 • with levitation on-ground • GOCE/GRACE concept • 2 ultra-sensitive axes • 1 less-sensitive axis • 1 angular acceleration measure • Analogic or Digital control loop

  6. Improved GOCE solution Linear Acceleration • With 4 accelerometers: • aX given by ¼(aX1+aX2+aX3+aX4) • aY given by ½(aY1+aY3) • aZ given by ½(aZ2+aZ4) • Improvement wrt GOCE: • Temperature stability

  7. Improved GOCE solution X Z Y Angular Acceleration From linear accelerations From angular accelerations in spacecraft reference frame in S/C ref. frame in accelerometer reference frame

  8. Improved GOCE solution Angular Acceleration From Linear acceleration From Angular acceleration • Limitation LS axis: • Detector noise (limited by range = ±6 µm) • Contact Potential Difference • Gold wire damping

  9. Improved GOCE solution Temperature stability Scale factor Mechanical Temperature driven by accelerometer noise Tmec = 40 mK/Hz1/2 (1 mHz / f) Grad Tmec = 4 mK/Hz1/2 (1 mHz / f) Electronic Temperaturedriven by scale factor stability Telec = 40 mK/Hz1/2 (1 mHz / f) Range Control range 3.1 10-5 m/s2 Measurement range 6.4 10-6 m/s2 Bias • Improvement wrt GOCE: • Reference voltage of ADC2 Along Y (ACC 1, 3) 1.2 10-7 m/s2 Along Z (ACC 2, 4) 1.2 10-7 m/s2

  10. New concept for angular acceleration 55 mm (GOCE 70 mm) X Y Z • Cubic proof-mass for having 3 angular accelerations: • Proof-mass in PtRh10: 25x25x25 mm3, 0.315 kg • no more testable on ground • one linear & one angular freedom controlled by axis Other design Other design Additional studies are necessary

  11. Analogic control loop (GRACE) Advantages Consumption Size (FEEU electronic around ASH) Mass ASH with FEEU : 7.6 kg x 4 => 30.4 kg ICU* 3.7 kg x 4 => 14.8 kg 45.2 kg Consumption ASH with FEEU : 2.1 W x 4 => 8.4 W ICU* 7.1 W x 4 => 28.4 W 36.8 W * Could be reduced Digital control loop (GOCE) Advantages Detector/action redundancy K2 correction easy Mass ASH 5.2 kg x 4 => 20.8 kg FEEU 6.3 kg x 2 => 12.6 kg GAIEU 6.6 kg x 1 => 6.6 kg 40.0 kg Consumption FEEU 15 W x 2 => 30 W GAIEU 16.5 W x 1 => 33 W 63 W Improved GOCE solution Mass and power budget

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