KEYWORDS: Software engineering, Telescope instrument control software, Software development, Sensors, Polarimetry, Satellites, Interfaces, Process control
The eXTP (enhanced X-ray Timing and Polarimetry) mission is a joint large mission of the Chinese Academy of Sciences (CAS) and European partners designed to study the state of matter under extreme conditions of density, gravity and magnetism. One of the four major instruments on eXTP is the Wide Field Monitor (WFM) which consist of 3 pairs of coded mask cameras with a total combined Field of View (FoV) of 90×180 degrees at zero response. With its enormous FoV, a source localization accuracy of 1 arcmin and an energy range of 2-50 keV the primary objective of the WFM is to provide triggers for the pointing instruments on the eXTP with less than one day reaction time. Its large area and resolution will be enough to detect state changes in compact objects as well. The WFM instrument is controlled by the Data Handling Unit located inside the Instrument Control Unit. The challenging requirement of broadcasting time and end-position of the triggering event to end-users in 30s necessitates special on-board data processing software (the eXTP burst online trigger, or XBOT), a hardware that can perform such processing and associated control software that would feed the raw data from the cameras into the XBOT and relaying alerts to the on-board data handling unit on the spacecraft side. Moreover, the WFM software performs several tasks related to the science data preparation, telecommand and telemetry management, and control of the cameras utilizing four LEON4 processing cores of E698 PM SoC from OCE Technology. This presentation discusses the details of the processing hardware and the interaction between different software components of the WFM on eXTP.
The eXTP (enhanced x-ray timing and polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS), with a large involvement of Europe. The scientific payload of eXTP includes four instruments: the SFA (spectroscopy focusing array) and the PFA (polarimetry focusing array)—led by China —the LAD (large area detector) and the WFM (wide field monitor)—led by Europe (Italy and Spain). They offer a unique simultaneous wide-band x-ray timing and polarimetry sensitivity. The WFM is a wide field x-ray monitor instrument in the 2-50 keV energy range, consisting of an array of six coded mask cameras with a field of view of 180°x90° at an angular resolution of 5 arcmin and four silicon drift detectors in each camera. Its unprecedented combination of large field of view and imaging down to 2 keV will allow eXTP to make important discoveries of the variable and transient x-ray sky and is essential in detecting transient black holes, that are part of the primary science goals of eXTP, so that they can be promptly followed up with other instruments on eXTP and elsewhere.
THESEUS (Transient High Energy Sky and Early Universe Surveyor) is one of the three missions selected by ESA as fifth medium class mission (M5) candidates in its Cosmic Vision science program, currently under assessment in a phase A study with a planned launch date in 2032. THESEUS is designed to carry on-board two wide and deep sky monitoring instruments for X/gamma-ray transients detection: a wide-field soft X-ray monitor with imaging capability (Soft X-ray Imager, SXI, 0.3 – 5 keV), a hard X-ray, partially-imaging spectroscopic instrument (X and Gamma Imaging Spectrometer, XGIS, 2 keV – 10 MeV), and an optical/near-IR telescope with both imaging and spectroscopic capability (InfraRed Telescope, IRT, 0.7 – 1.8 μm). The spacecraft will be capable of performing fast repointing of the IRT to the error region provided by the monitors, thus allowing it to detect and localize the transient sources down to a few arcsec accuracy, for immediate identification and redshift determination. The prime goal of the XGIS will be to detect transient sources, with monitoring timescales down to milliseconds, both independently of, or following up, SXI detections, and identify the sources performing localisation at <15 arcmin and characterize them over a broad energy band, thus providing also unique clues to their emission physics. The XGIS system consists of two independent but identical coded mask cameras, arranged to cover 2 steradians. The XGIS will exploit an innovative technology coupling Silicon Drift Detectors (SDD) with crystal scintillator bars and a very low-noise distributed front-end electronics (ORION ASICs), which will produce a position sensitive detection plane, with a large effective area over a huge energy band (from soft X-rays to soft gamma-rays) with timing resolution down to a few µs. Here is presented an overview of the XGIS instrument design, its configuration, and capabilities.
The X and Gamma Imaging Spectrometer instrument on-board the THESEUS mission (selected by ESA in the framework of the Cosmic Vision M5 launch opportunity, currently in phase A) is based on a detection plane composed of several thousands of single active elements. Each element comprises a 4.5×4.5×30 mm3 CsI(Tl) scintillator bar, optically coupled at both ends to Silicon Drift Detectors (SDDs). The SDDs acts both as photodetectors for the scintillation light and as direct X-ray sensors. In this paper the design of the XGIS detection plane is reviewed, outlining the strategic choices in terms of modularity and redundancy of the system. Results on detector-electronics prototypes are also described. Moreover, the design and development of the lownoise front-end electronics is presented, emphasizing the innovative architectural design based on custom-designed Application-Specific Integrated Circuits (ASICs).
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