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ANITA Navigation and Orientation

ANITA Navigation and Orientation. Kurt Liewer. High Level Requirements. Position (navigation) Position knowledge error < 10 m/axis required for calibration pulse timing Science requirements ( D E/E and source localization) are not called out but 1 km is probably adequate Orientation

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ANITA Navigation and Orientation

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  1. ANITA Navigation and Orientation Kurt Liewer Collaboration Meeting at UCI, April 7-9, 2005

  2. High Level Requirements • Position (navigation) • Position knowledge error < 10 m/axis • required for calibration pulse timing • Science requirements (DE/E and source localization) are not called out but 1 km is probably adequate • Orientation • azimuth knowledge error < 1.4° • for localization of known sources • for map reconstruction • pitch/roll knowledge error < 0.7° • from requirements on energy determination (range) Collaboration Meeting at UCI, April 7-9, 2005

  3. Navigation Instrumentation • Thales ADU5 GPS receiver • previously used by NSBF (CREAM) • accuracy 5 m/axis • Thales G12 GPS receiver • used on ANITA-light • accuracy 5 m/axis • pressure sensor • provides redundant altitude information • NSBF GPS receiver • More than enough accuracy and redundancy • Extrapolation would be adequate for science requirements for extended periods (hours) of GPS loss of signal Collaboration Meeting at UCI, April 7-9, 2005

  4. Pointing Budget Collaboration Meeting at UCI, April 7-9, 2005

  5. Orientation Instrumentation • Thales ADU5 GPS receiver in differential mode with 3 m baseline • previously used by NSBF (CREAM) • accuracy 0.06° in azimuth (heading) • accuracy 0.12° in pitch and roll • accuracy values are for 3 m baseline, no multipath and no dilution of precision • On CREAM the dilution of precision ranged from 2 to 6 • average DOP ~3 • CREAM (and BOOMERANG) have periods of loss of GPS but it is unknown (to me) if this is a loss of GPS signal or a loss of telemetry • CREAM angle noise roughly matches expectation but has long term (hundreds of seconds) variations that seem unlikely to be real Collaboration Meeting at UCI, April 7-9, 2005

  6. Orientation Data Twenty minutes of BOOMERANG pointing data Std dev of pitch = 0.04° std dev of roll = 0.02° Note the change between the pitch/roll scale and the azimuth scale Collaboration Meeting at UCI, April 7-9, 2005

  7. Orientation Data Collaboration Meeting at UCI, April 7-9, 2005

  8. Orientation Instrumentation (cont’d) • Sun sensor • covers ±22.5° in azimuth and 0° to 45° in elevation • Sun angle error < 0.5°/axis • slightly modified version of the Sun sensor flown on Anita-light • Does not unambiguously give azimuth and elevation • insensitive to rotation about direction to Sun • Crossbow CXL02TG3 3-axis accelerometer • two units flown with a vertical separation to allow identification angular acceleration (pendulum modes) • can not separate out effects of linear acceleration and pitch/roll • sensitivity ~ 10-3 G Collaboration Meeting at UCI, April 7-9, 2005

  9. Orientation Instrumentation (cont’d) • Crossbow CXM539 3-axis magnetometer • magnetic field thought to be too poorly known and too variable for direct measurement of angles • can be used to measure fluctuations in angles • calibration of fixed magnetic field may not be possible • Combined measurements from all secondary sensors may provide adequate performance Collaboration Meeting at UCI, April 7-9, 2005

  10. Concerns • Navigation • None • Orientation • Primary sensor (differential GPS) may have outages • secondary sensors are on the edge of not meeting requirements • in flight calibration difficult • can cross compare at some level • structure deformation due to temperature may affect interpretation Collaboration Meeting at UCI, April 7-9, 2005

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