The CanX-7 ADS-B Mission: Signal Propagation Assessment ()
ABSTRACT
The CanX-7 Automatic Dependent Surveillance-Broadcast
(ADS-B) nanosatellite mission collected more than four million ADS-B messages
between October 2016 and April 2017. An analysis of data collected over the
north Atlantic Ocean from 05 to 28 Oct included 20,707 position messages in
which the angle from satellite nadir to aircraft was determined. The proximity
of the received signal strength to the noise floor of the sensor allowed for an
analysis of optimal aircraft-satellite orientation for ADS-B transmission
detection. The results showed a significant disparity between descending and
ascending passes of the satellite. For descending passes, the
average nadir angle was 50.1° with 90% of the contacts greater than 40°. The ascending passes had an average nadir angle of 31.6° with only 24.8% of the contacts exceeding 40°. The evidence suggests that the satellite
magnetic torquer may not have been fully aligned with the north magnetic pole
as the satellite moved northward, resulting in ascending pass nadir angles that
were not reflective of the full range of values. Further analysis of the
descending passes showed agreement with an ADS-B signal propagation model with
peak reception at nadir angles of 51° ± 8°. For space-based
ADS-B operations, the results support the replacement of the current aircraft upper
quarter-wave monopole to an antenna that will transmit more energy directly
above the airframe.
Share and Cite:
Vincent, R. and Freitag, K. (2019) The CanX-7 ADS-B Mission: Signal Propagation Assessment.
Positioning,
10, 1-15. doi:
10.4236/pos.2019.101001.