University of Bern, April 1011

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IBEX SWTM
IBEX-loStar Sensor Eberhard Möbius, UNH
University of Bern, April 10-11
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Star SensorKey Requirements Drivers

• Star Sensor is Key to provide a direct reference
  to Stars for the ISM O Flow Direction
• Thus it is to provide directions to 100 Stars
  within lt0.1o relative to thee IBEX-Lo Optics
  Deck(lt 0.1o vs. Collimator Mounting Plane IBEX
  Lo-739)
• Sensitivity down to Mag 2.5 Stars (3.5 goal)
  Sensitivity adjustable to Jupiter and Moon

Spin
Separation yields Elevation of Star
In Spacecraft Coordinates
Timing yields Azimuth of Star
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Star Sensor Calibration (Results)

• Star Sensor Calibrated Mag 4 - -2

• Works even up to Mag -11 Further Refining FS
  Tests planned

• Star Position can be determined to better
  than 0.03o (with 10 noise on PMT Signal)

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Star Sensor maintained Pointing after Vibration

• After Vibration of the Star Sensor

• Absolute Pointing of the Star Sensor not
  changed by more than 0.05o
• Response of PMT has not changed

Signal V
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Star Sensor Data Stream

• 8 Bit PMT Signal Voltage every 0.5 sec (exact
  value in Electrical Reference Document)
• Timing to be counted from Sun Pulse for each
  Spin
• CEU accumulates these data into Histogram
• Data contain- multiple Stars- diffuse
  background

1 Star Signal
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Needed Databases

• Star Catalog down to Magnitude 5
• Diffuse Background DataThis is available at
  Ruhr-Universität BochumGeorge Clark, UNH
  student, will visit RUB in summer 2008 to refine
  the data set for the Star Sensor response
• Ancillary Catalogues should be transformed into
  actual S/C coordinates for each orbit

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Star Sensor Assembly Method

• Optical Column Assembly
• Common Vendor (Tecomet) aperture Etch column
  EDM
• Near zero clearance fits and orthogonal
  alignment
• Mounting of Star Sensor
• On Optics Deck with Optical Column Flange
• PMT Board Installation in Separate Case
• Light Tight mating of Optical Column PMT Case
• Ground Isolation
• PMT and PMT Board
• Apertures and Optical Column
• Housing and Light Tightness