A new algorithm for optical observations of space debris with the TAROT telescopes

International audienceSince 2004, we observe satellites in the geostationary orbit with a network of robotic ground based fully automated telescopes called TAROT. One of them is located in France and the second at ESO, La Silla, Chile. The system processes the data in real time. Its wide field of view is useful for the discovery, the systematic survey and for the tracking of both catalogued and un-catalogued objects. We present a new source extraction algorithm based on morphological mathematic, which has been tested and is currently under implementation in the standard pipeline. Using this method, the observation strategy will correlate the measurements of the same object on successive images and give better detection rate and false alarm rate than the previous one. The overall efficiency and quality of the survey of the geostationary orbit has drastically improved and we can now detect satellites and debris in different orbits like Geostationary Transfer Orbit (GTO). Results obtained in real conditions with TAROT are presented

CADOR and TAROT: a virtual observatory

International audienceTAROT (Telescope Action Rapide pour les Objets Transitoires - Rapid Action Telescope for Transient Objects) is a network of two robotic ground based telescopes. The telescopes are fully automated, from the scheduling of the observation requests to the processing of the data. All the applications use a specific automated processing pipeline which has been continuously improved. CADOR (Coordination et Analyse des Donnees d'Observatoires Robotises - Coordination and Data Analysis of Robotic Observatories) is a set of data base servers which manage TAROT telescopes. CADOR is the prime interface to request new observations from TAROT and to access all images saved with the possibility to make additional processing and analysis. Tarot and Cador are compliant with Virtual Observatory standard and protocols

Remote steering of OCA local time scale using UTC(OP)

International audienceIn October 2012, the Ge?oazur TF laboratory in OCA has been reorganized to improve signal distribution stability. In particular we have implemented a new time scale TA(OCA) based on H-maser T4Science. The H-maser frequency is steered with an HROG-10 microphase stepper. The correction applied is computed every day taking into account the frequency of the free running maser and the actual time difference between TA(OCA) and UTC(OP). The main idea is to keep the time difference between our local time scale TA(OCA) and UTC below 50 ns, in order to time tag the SLR laser pulses and to have an error below 1 mm for distance measurement between satellite and laser station

Robotic Observations of the Sky with TAROT: 2004--2007

International audienceThe TAROTs (Télescopes à Action Rapide pour les Objets Transitoires; Rapid Action Telescopes for Transient Objects) are two fully robotic observatories designed to observe the early transient optical counterpart of gamma-ray bursts (GRBs). As their occurrence is rare, we also use TAROT to observe various other celestial objects: RR Lyrae stars, minor planets and supernovae. In this paper, we describe the telescopes, their networking, and the data-processing methods used

Link calibration against receiver calibration time transfer uncertainty when using the Global Positioning System

International audienceWe present a direct comparison between two different techniques for the relative calibration of time transfer between remote time scales when using the signals transmitted by the Global Positioning System (GPS). In the remote sites, the local measurements are driving either the computation of the hardware delays of the local GPS equipment with respect to a given reference GPS receiver, a receiver calibration, or the computation of a global hardware offset between two distribution reference points of the remote time scales, a link calibration. Both techniques do not require the same measurements on site, and we discuss the uncertainty budget computation differences. We report on one calibration campaign organized during Autumn 2013 between Observatoire de Paris (OP), Paris, France, Observatoire de la Côte dAzur (OCA), Plateau de Calern, France, and NERC Space Geodesy Facility (SGF), Herstmonceux, United Kingdom. We show the different ways to compute uncertainty budgets, leading to improvement factors of 1.2 to 1.5 on the hardware delay uncertainties when comparing the relative link calibration to the relative receiver calibration

Accuracy validation of T2L2 time transfer in co-location

International audienceThe Time Transfer by Laser Link (T2L2) experiment has been developed in close collaboration between Centre National d'Etudes Spatiales and Observatoire de la Côte d'Azur. The aim is to synchronize remote ultra-stable clocks over large-scale distances using two laser ranging stations. This ground to space time transfer has been derived from laser telemetry technology with dedicated space equipment designed to record arrival time of laser pulses on board the satellite. For 3 years, specific campaigns have been organized to prove T2L2 performance. In April 2012, we performed a 2-week campaign with our two laser ranging stations, Métrologie Optique and French Transportable Laser Ranging Station, to demonstrate the T2L2 time transfer accuracy in co-location. We have compared three independent time transfer techniques: T2L2, GPS, and direct measurement, with both an event timer and an interval counter. The most important result obtained in this campaign was a mean agreement between T2L2 and a direct comparison better than 200 ps. This is the first major step to validate the uncertainty budget of the entire T2L2 experiment. This paper focuses on this campaign setup and the obtained results

Link calibration against receiver calibration time transfer uncertainty when using the Global Positioning System

International audienceWe present a direct comparison between two different techniques for the relative calibration of time transfer between remote time scales when using the signals transmitted by the Global Positioning System (GPS). In the remote sites, the local measurements are driving either the computation of the hardware delays of the local GPS equipment with respect to a given reference GPS receiver, a receiver calibration, or the computation of a global hardware offset between two distribution reference points of the remote time scales, a link calibration. Both techniques do not require the same measurements on site, and we discuss the uncertainty budget computation differences. We report on one calibration campaign organized during Autumn 2013 between Observatoire de Paris (OP), Paris, France, Observatoire de la Côte dAzur (OCA), Plateau de Calern, France, and NERC Space Geodesy Facility (SGF), Herstmonceux, United Kingdom. We show the different ways to compute uncertainty budgets, leading to improvement factors of 1.2 to 1.5 on the hardware delay uncertainties when comparing the relative link calibration to the relative receiver calibration

Calibration of the TWSTFT link between OCA and OP using a GPS link calibration

International audienceThree independent time transfer techniques are in use in Observatoire de la Côte d'Azur (OCA): GPS, TWSTFT and T2L2. In Autumn 2013, a GPS receiver relative calibration campaign has been carried out. The result of this campaign, primary intended to compare GPS with T2L2, have allowed the calibration of the TWSTFT link between OCA and OP. We computed for OCA the value of CALR = -7111.9 ns, with an uncertainty U= 2.8 ns at k=2. From this calibration we caracterise the others links with the triangle closure technique

T2L2: 6 years of sub-nanosecond time and frequency metrology

International audienceThe Time Transfer by Laser Link (T2L2) experiment aims at achieving ground to ground time transfer between remote clocks using time tagging of laser pulses. The principle is derived from laser telemetry technology with a dedicated space equipment designed to record arrival epoch of laser pulses at the satellite. The use of laser pulses, instead of microwave signals, allows realizing some time transfer with time stability of a few picoseconds and accuracy better than 150 ps. The mission is mainly dedicated to the metrology of time and frequency, nevertheless the objectives are multiple. First technological, T2L2 will demonstrate the feasibility and the performance of the time transfer by laser link. Then scientific, the expected performances of T2L2 will allow ultimate comparisons with microwave system or to perform some fundamental physics tests.Initially planned for duration between 2 and 3 years, the mission has just passed through 6 years in operation. These 6 years of missions, punctuated by several specific campaigns of measurements, allowed filling the major part of the assigned objectives. Through the story of these 6 years of missions, this paper will redraw the main results, from the first estimations of stability of the ground to space time transfer to the absolute direct comparison with GPS Common-View, consistent to 240 ps or below over continental baselines