Manuel Pavy, CNES; Pascal Richard, CNES; Emmanuel Delande, CNES; Sébastien Théron, Magellium
Keywords: Operational system, performance, cataloguing, telescope, orbit restitution, image processing
Abstract:
Improving the operational signal processing chain for faster acquisition of new objects to the French National Catalogue of orbital objects.
Manuel Pavy
SSA specialist, CNES
Emmanuel Delande
SSA specialist, CNES
Pascal Richard
SSA Expert, CNES
Sébastien Théron
Image processing expert, Magellium
ABSTRACT
Maintaining and updating the French national catalogue of space objects involves several components. Those that are primarily focused on the GEO regime are closely intertwined and span across the full signal processing chain:
1) The TAROT (Télescope à Action Rapide pour les Objets Transitoires, i.e, fast telescope for transitory objects) network provides the brunt of the images of the GEO belt;
2) The TRITON (new image processing from optical images) software extracts objects detected in each TAROT image, and provides their angular coordinates from astronomic calibration;
3) The OSMOSE (Observation des Satellites, Mesures et Orbites pour la Surveillance de l’Espace, i.e., observation of satellites, measurements and orbits for space surveillance) software suite maintains an up-to-date catalogue of space objects through the processing of the TRITON detections, and schedules the TAROT sensors for surveillance activities or targeted data acquisition.
The national catalog producer system is composed on 4 main components and form a ground system, data communication and control of remote telescopes come with many challenges:
Figure – IT system and life cycle of OSMOSE products from TAROT and TRITON
The national catalogue producer system form a IT system which interact with remote telescopes to control them and retrieve products from them. The target new functionality which consists on the ability to track new objects and catalogue them in the same night is a real challenge: running the full signal processing altogether which is a complex, time-consuming task and that involves the daily update of about 500 catalogued objects in a reduced time.
The figure below describes the architecture of the system and the figure above show the workflow of the measurement production. First, a TAROT telescope takes 3 successive photos, then processed by TRITON to extract of the presence of objects, or detections, in each photo. OSMOSE then retrieves these detections, links them into tracklets, and tries to associate them to objects already identified in the catalogue. If the last step fails, then OSMOSE must compute an initial orbit estimate from orphan tracklets, then task the telescope network into observing the whereabouts of the potential object to confirm its existence through further observations.
Figure – Worklow of the OSMOSE processing chain
The paper will present several key improvements that were implemented, spanning across the full signal processing chain, in order to bring down the typical duration between the first detection of a new object, and the scheduling of subsequent observation strategies aiming at confirming its presence, from 3 hours to about 20 minutes.
The paper will present in a first part the ensemble composed by the OSMOSE cataloguing system, the TAROT telescopes and the TRITON image processing software. In a second part, it will present the challenges which have to be tackled and how the system has been modified to improve the velocity and accuracy of the operational processing chain. Finally, it will show how this improvement allow the integration of new objects in the catalogue, and paves the way for a future tasking strategy adapted to the upcoming integration of a new telescope to the TAROT network.
The first key improvement relates to the overhaul of the transmission protocol between the TAROT telescopes — TAROT Calern (TCA) in metropolitan France, Tarot Chili (TCH) in Chile and Tarot Réunion (TRE) in the Réunion island — and the OSMOSE system. Owned by the CNRS and partially exploited by the CNES for SSA activities, these telescopes are located in remote areas and must rely on limited bandwidth for data transmission. The paper will explain how the volume of transmitted data has been reduced to address the connectivity constraints, without hampering the overall quality of the information to be subsequently processed by OSMOSE.
The second improvement relates to the processing of the TAROT images by the TRITON software, one of the most resource-intensive tasks within the processing chain. The principle of TRITON is to extract the brightest stars from the TAROT image, and link them to a star catalog in order to a) correct the deformation of the image induced by the mirror through a polynomial transformation and, then, b) extract objects from the image and provide angular pairs (right ascension and declination) for every such detection. The paper proposes a method substituting the full catalog of stars with a simplified one, in order to fasten up the processing of the TAROT images.
The last improvement deals with the overhaul of the orbit determination step, another major resource-intensive task in the processing the OSMOSE software suite, only briefly covered in this paper as it was the topic of recently published work. The traditional approach, producing orbit estimates through least-square methods on 20-day-long observation arcs largely overlapping between two successive tracks, is replaced with a sequential scheme involving tracks produced with a least-square method on 3-hour-long observation arcs, processing only observations posterior to the initial track and bootstrapped with the initial track’s covariance.
Finally, the paper will then show how these various improvements expanded the abilities of the catalog to detect and incorporate new objects. Thanks to the improved reactivity of the overall processing chain, OSMOSE is then typically able to schedule further observations of a new object the same night it was detected, such that a confirmed object can be added to the catalogue more consistently, and with an orbit estimate of better quality.
Date of Conference: September 19-22, 2023
Track: SDA Systems & Instrumentation