APS Formation Sensor

1
APS Formation Sensor

• ISAL Study Overview
• Dr. H. John Wood
• 15 March 2002

2
Introduction

• This work is relevant now because of the advent
  of many new instrument concepts for
  constellations of spacecraft at the Earth-Sun L2
  point
• The study is relevant to you with specific
  interests for Stellar Imager and MAXIM
• We hope to show you today how ISALs engineering
  team has found the solution to the challenging
  problem of measuring the relative positions of
  five daughter spacecraft to 3mm at a distance
  of 50 km
• This objective will be met through nine diverse
  discipline engineering studies reported today

3
Overview of Key Results

• The formation sensor can be built using todays
  technology and feasible extension of state of the
  art
• No tall poles are foreseen in the detector side
  or the laser beacon side
• The system will be able to provide the required
  3mm precision in the knowledge of the daughter
  spacecraft from a distance of 50 km
• The system can be adapted to shorter distances
  such as that required for Stellar Imager or the
  longer distance as in the case of MAXIM
• The system can be used for constellations with
  more than five daughter spacecraft

4
Two Highlights

• Optics the design selected is a refractive
  aerial camera which is telecentric
• Telecentric means that the plate scale does not
  change with focus setting ideal for astrometric
  applications in space
• Detector CMOS technology means that the Active
  Pixel Sensor (APS) has individual pre-amplifiers
  on each pixel allowing readout of small
  subsections of the array for individual
  positional measurement of each daughter spacecraft