Dr. Paul Konkola (Textron Systems), Charles Crandall (Textron Systems), Tim Georges (Textron Systems), Robert Lercari (Textron Systems), Moe Tun (Advanced Technology Corp), Laura Ulibarri, Jill Watson (Air Force Research Laboratory)
Keywords: Lasers
Abstract:
The HI-CLASS (HIgh Performance CO2 LAdar Surveillance Sensor) operating in conjunction with the AEOS 3.6 meter aperture telescope atop Mt. Haleakala has demonstrated its ability to produce simultaneous precision range (4m in narrow band; 10 cm in wide band), range rate (< 0.25 m/s) and angular position measurements (FWHM beam width of 4 micro-radians) of both uncooperative ( > 0.1 – 0.2 m diameter) in LEO trajectories and cooperative (retro) satellites. We describe key improvements to the system that help extend the systems range accuracy toward its precision. The limiting range-rate error source is also addressed.
The system time base has been upgraded. The method and results for calibrating the time base and measuring timing errors over the full time of flight are presented. The upgraded timebase error has been demonstrated to be better than a part per billion when referenced against a second calibrated clock.
HI-CLASS is a heterodyne system and requires filter calibrations to compensate for the group delay inherent in the electronic channels of the out-going pulse monitor (OPM) and the received signals. These signals have a varying frequency on a pulse-to-pulse basis that is largely dependent on the local oscillator-to-seed locking stability and the Doppler shift from the target that is un-cancelled electronically. The method and procedure for calibrating the group delay for both the OPM and the receiver channels is presented.
The range-rate precision and accuracy has been assessed to be limited by the stability of the local oscillator during the time of flight. This assessment is supported by cm/s level noise floor measurements at short range. Also the stability of the local oscillator when referenced against a Freed ultrastable laser is consistent with the velocity noise floor measured against space objects when considering the time of flight. Data is presented for velocity measurements that are corrected using the signal from the ultrastable laser and the local oscillator beat.
HI-CLASS metrics are compared to the truth trajectories derived from the International Laser Ranging Service data. This cm-level accurate assessment method is used to demonstrate the improvements.
Date of Conference: September 10-14, 2006
Track: Lasers