If you’ve read the detailed timeline for Sentinel-2A launch on 23 June, you will have noticed an interesting set of entries for Perth towards the end, namely:
- MET 50:29 – Earliest AOS Vega – PER AOS VEGA
- MET 55:20 – Earliest AOS S2 – PER Acquisition of signals from S2A
Yes: ESA’s 15-m diameter Perth tracking station will acquire signals (AOS) from both the Vega launcher’s AVUM upper stage just a few minutes prior to separation and from Sentinel-2 just moments after separation.
We asked Estrack network engineer Gerhard Billig, normally based at ESOC but now in Australia to support the launch, to explain a bit about this.
The Perth ground station will track the final burn of the Vega upper stage, which is the orbit injection burn, as well as the spacecraft separation shortly after. These important events will be received/monitored via telemetry from the launcher.
While continuing to track the launcher, other systems of the PER ground station will be configured to receive signals from the spacecraft, which starts transmitting after separation, and will provide a telecommand uplink for the mission controllers at ESOC as well as radiometric measurements (i.e. ranging data).
Tracking the launcher in parallel to the spacecraft also helps increase robustness for the first acquisition of the satellite, which is a critical moment in the satellite’s LEOP.