High-Performance Accelerometer for On-Orbit Autonomy

Objectives

The objective of this activity is to assess the feasibility of a high-resolution accelerometer in order to increase the station keeping autonomy in relation with the electric engine of the @BUS platform.


The accelerometer would be used to measure the East/West drift of the satellite during the North/South thrusts. It would permit to define in real-time the maximum North/South thrust time in order to obtain an acceptable East/West drift while not requiring control from ground stations.

Challenges

The key issues of the study are:



  • The compatibility of the mechanical concept with the launch vibration,



  • The compatibility of the accelerometer servo-control with the flight micro-vibration environment,



  • The design of a concept that matches the requirements of compactness in terms of mass, volume and power consumption.

Benefits

The current project will lead to the implementation of a versatile and high-performance accelerometer exhibiting nano-g resolution.

It will permit the availability of an off-the-shelf accelerometer solution with outstanding performance:



  • Acceleration sensed along 3 translation axes,

  • An operating range covering 5 orders of magnitude from 2×109 g to 5×104g The accelerometers will fit in a compact packaging:

  • Small volume of 1.5dm3, 15cm×10cm×10cm,

  • A total mass lower than 2kg,

  • A total power consumption of 6W including the DC/DC converters, with a ready-to-use integrated MIL-STD-1553B interface.

The accelerometers will be manufactured with space-qualified parts and in accordance with the ESA procedures to achieve a high-reliability instrument with a life duration compatible with the telecom requirements.

The instrument is delivered after series of tests and calibrations.

Features

The accelerometer is servo-controlled and electrostatic.







click for larger image


It is based on the electrostatic levitation of a 20g proof-mass inside an electrode cage. Capacitive position sensors detect the displacements of the proof-mass, deliver the information to the servo-control which in turn maintains the proof-mass at the centre of the cage by applying the appropriate potentials on the electrodes.


The mechanical core is mounted on a reference sole plate and enclosed in a hermetic housing. The front-end electronics surrounds the housing: it consists of 6 capacitive sensors and 6 analog correcting networks for controlling the motion of the proof-mass along the 6 degrees of freedom.



The acceleration analog estimate is digitised and transmitted to the satellite through a MIL-STD1553B bus.

Plan

The activity focuses on the concept definition and performance model of the accelerometer including:



  • Preliminary global architecture (with respect to the mechanical and electronic parts),



  • Sensor dimensioning (with respect to the mechanical and thermal environment),



  • Demonstration of the launch mechanical loads withstanding without locking device,



  • Definition of operational environmental envelope (mechanical, EMC/ESD, magnetic, thermal),



  • Establishment of a mathematical model for system analysis (including noise PSD, bias and scale factor, stability and non linearity).

Current status

The first phase of the activity has been successfully completed, showing the feasibility of a new concept using accelerometers for increased on-orbit autonomy. For Alphabus an alternative option has been chosen to achieve on-orbit autonomy, and it has therefore been decided not to pursue the activity.

Status date

Monday, June 26, 2006 - 12:06