You might have seen the wonderful radar images of ATV flying over Earth after its launch last week. Jean-Michel Bois, Nathalie Védie and Laurent Arzel from ESA and Dr.-Ing. Thomas Patzelt, Dr.-Ing. Jens Rosebrock and Dr.-Ing. Ludger Leushacke from Fraunhofer got together to explain the background on these images:
ESA’s ATV Toulouse Operations requested High frequency physics and Radar support from the German Fraunhofer institute to track ATV during its first orbits after separation from its Ariane 5 launcher. The goal is to provide information on the ATV injection and orbit parameters and to assess ATV’s configuration for the Flight Dynamics team. In particular the flight dynamics team was interested in the deployment ATV’s solar panels and of the ADB/KBM boom in the first minutes after the separation.
The ADB/KBM boom supports ATV’s Proximity Link Transceiver used during the rendezvous phase to exchange data with its counterpart on the International Space Station. This data allows for relative navigation between ATV and the Space Station and provides crew monitoring and control of the ATV during docking.
For ATV-2 and ATV-3, the full deployment and lock of this boom were not confirmed by telemetry data, so the final boom position was never confirmed.
To answer this question the Fraunhofer Institute was asked to image the spacecraft using TIRA radar data analysis.
Tests were performed during ATV-3’s free-flight days before its destructive reentry to validate the feasibility of the system, the quality of the radar images and coordination between ATV-CC and Fraunhofer teams and also to check potential ATV attitude changes to optimise the observation conditions for radar imaging, if necessary.
In parallel, a tool was developed by the ESA ATV Operations Division (Nathalie Védie and Laurent Arzel) to reproduce ATV’s orientation in a virtual radar image by projecting a wire-frame model on the radar image plane. Based on real trajectory and ATV attitude telemetry data during the path over the Fraunhofer’s radar station, the virtual wire-frame ATV image can be compared with the radar image. It allows a validation of the ATV configuration and a rejection of the bright radar image pixels due to noise or image generation artefacts.
The combination of the images is a powerful way to assess ATV’s configuration in space. The figures show that the projected image fits perfectly with the radar image.
ATV-4 imaged by radar with wire grid superimposed Credit: ESA/Fraunhofer FHR institute
ATV-4 imaged in orbit 8 June
A fabulous mix of images taken by Ralf Vandebergh showing exquisite detail of the ATV in orbit on 8 June 2013. Ralf wrote:"No illumination of the solar panels but amazing visibility of segment structure in the ATV!" Thanks for sharing, Ralf!
ATV-4 mission report 13 June
ATV is operating as expected; all systems nominal. On 13 June, ATV-CC completed the docking probe pull-out test at 16:14 CEST (ATV's docking system is now ready for contact with Station). Next activity 14 June: TIV (transfer to ISS vicinity) manoeuvres; first boost set for 13:13 CEST.
Jean-Michel Bois, Head of the ESA Operations Team at ATV-CC, notes:
The ATV probe extension activity was successfully performed on 13 June at 14:30 GMT. This task prepares the ATV for the docking on 15 June. The probe detects the contact with the ISS Service Module port; then, by retraction, performs the mechanical link-up between ATV and ISS.
Final days of preparation for the arrival of ATV-4
ESA's Volare mission director Roland Luettgen's latest update on ATV-4 preparations from an astronaut perspective.
Although astronauts are well trained for the arrival of ESA’s supply ship ATV-4, they are spending time these days to refresh their knowledge, to make sure they are ready.
The main astronaut task during the rendezvous and docking of ATV Albert Einstein is monitoring the spacecraft’s automated approach and reacting in case of problems.
The monitoring will start on Saturday at around 09:50 GMT when ATV-4 is still more than 15 km away from the International Space Station. Until then the crew, and in particular Luca, are preparing everything for Albert Einstein’s arrival. We expect some spectacular video and images taken when ATV-4 is closing in at about 1 km distance from the Station.
During the final approach, the International Space Station and ATV-4 will pass through day and night several times as they travel at speeds of more than 28 000 km/h. At this speed they fly around Earth every 90 minutes.
Once ATV Albert Einstein has arrived, the crew will start preparing to enter the spaceship on Monday and getting ready to unload the cargo. Luckily they are in space and gravity does not pull at them, so transferring several tons of cargo is not ‘heavy’ work. We have planned to have the first major science experiment, FASES, moved out of ATV-4 and installed into the Columbus laboratory on Tuesday next week.