Citation
Abstract
Many deep space missions retransmit received uplink signals back to Earth in order to enable round-trip light time measurements. These measurements are used to calculate the spacecraft’s distance to Earth, and the retransmission channel is referred to as a turnaround ranging channel. During downlink tracks, Deep Space Network antennas are repetitively scanned in a conical pattern to cause small changes in residual carrier signal-to-noise ratio. The antenna pointing error can be inferred from these changes. Shortly after launch, turnaround ranging channel uplink noise can dominate noise power in the downlink signal, which results in noise power that shifts to match residual carrier power changes during a conical tracking scan. When turnaround noise dominates downlink noise, the carrier signal-to-noise ratio does not change over a conical scan, and the pointing error estimate is ruined. The dominant turnaround noise appears on a power spectrum as a pedestal raised above the downlink noise floor, so the phenomenon is named the “pedestal effect”. The pedestal effect is studied here in detail, and an algorithm for mitigating the pedestal effect is proposed.
Keywords
Details
- Volume
- 42-227
- Published
- November 15, 2021
- Pages
- 1–19
- File Size
- 737.8 KB