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Precision Photometric Calibration Using Balloon-Borne Light Source

Develops technique for real-time aerosol extinction measurement & precise photometry for 1a Supernova surveys. Balloon payload integrates NIST photodiodes, lasers, and optical systems for accurate readings. Demonstrates flight control and thermal management challenges.

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Precision Photometric Calibration Using Balloon-Borne Light Source

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  1. A Balloon Borne Light Source for Precision Photometric Calibration Maxwell Fagin Dartmouth College FermiLab, April 2012

  2. Atmospheric Aerosol Extinction Goal: Provide a technique for real time measurement of aerosol extinction and enable <1% photometry for 1a Sn surveys. Type 1a Supernova are the primary photometric standard in Cosmology Background A principal source of photometric error:

  3. 1) Backlight atmosphere with balloon borne polychromatic light source Technique 2) On board NIST photodiode to measure absolute mag of source 3) Ground based NIST photodiode to measure apparent mag at detector 4) Account for extinction due to H20 and molecular scattering with MODTRAN 5) Remaining difference due to aerosol extinction

  4. Balloon Payload Integrating Sphere NIST Photodiode #1 10 mW Lasers 440 nm 532 nm 639 nm 808 nm Well characterized Lambertian Profile Known View angle NIST Photodiode #2 Telescope NIST defined spectral response Technique

  5. Repeatedly fly the payload over an observatory Technique Use as a photometric standard to produce a catalogue of White Dwarfs

  6. Payload Design • Optical Systems • Lasers (4) • Integrating Sphere • Communication Systems • GPS • Telemetry • ELT radio beacon • Instrumentation/Sensing • NIST Photodiode • Attitude • Support Systems • Power • Cutdown • Recovery Total weight < 6 lbs

  7. Optical Systems • Lasers (4) • Integrating Sphere • Communication Systems • GPS • Telemetry • ELT radio beacon • Instrumentation/Sensing • NIST Photodiode • Attitude • Support Systems • Power • Cutdown • Recovery Payload Design Total weight < 6 lbs

  8. Integrating Sphere Optical Systems Laser Diodes Photometric stability <.5% 100 g, <.5 W per laser

  9. Optical Systems Mass and optical mockup used in all flights to date

  10. 900 MHz (UHF) DNT Transceiver Radio Communication Systems Robust, but line of sight communication only

  11. Mag/Accelerometer for real time attitude data Instrumentation/Sensing

  12. Peak Cooling Ascent: airspeed 5 m/s through 30% atm at -55 °C Peak Heating Floating: airspeed 0 m/s in 2% atm at -45 °C Challenge: Thermal Management

  13. Demonstration Flight: ALTAIR 12011

  14. Demonstration Flight: ALTAIR 204/13/2012

  15. ALTAIR 2 Results04/13/2012 Demonstrated: Ability to control flight profile

  16. ALTAIR 2 Results04/13/2012 Demonstrated: Ability to maintain payload at normal temperatures

  17. ALTAIR 2 Results04/13/2012 Demonstrated: Measure payload’s real time attitude

  18. Still to do: • Imaging from ground station • Replace mockup optics with flight hardware • Zero pressure float balloon • Night launch • Payload interior maintained between 0-40°C • Sufficient power for >2 hour of flight • Control, communication and data handling • Cutdown and separation from balloon (pending recovery) • Telescope and radio tracking • Launch and recovery logistics Goals Completed:

  19. Thanks to: Yorke Brown, Chris Stubbs, Kristina Lynch and Justin Albert Questions?

  20. Flights: GreenCube 3, GreenCube M(2010)

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