法国国家太空研究中心
The X-ray Integral Field Unit is the X-ray imaging spectrometer on-board one of ESA's next large missions, Athena. Athena is set to investigate the theme of the Hot and Energetic Universe, with a launch planned in the late-2030s. Based on a high sensitivity Transition Edge Sensor (TES) detector array operated at very low temperature (50 mK), X-IFU will provide spatially resolved high resolution spectroscopy of the X-ray sky in the 0.2-12 keV energy band, with an energy resolution goal of 4 eV up to 7 keV [3 eV design goal]. This paper presents the current calibration plan of the X-IFU. It provides the requirements applicable to the X-IFU calibration, describes the overall calibration strategy, and details the procedure and sources needed for the ground calibration of each parameter or characteristics of the X-IFU.
We introduce a fast method to measure the conversion gain in complementary metal-oxide-semiconductor active pixel sensors, which accounts for nonlinearity and interpixel capacitance (IPC). The standard “mean-variance” method is biased because it assumes that pixel values depend linearly on the signal, and existing methods to correct for nonlinearity still introduce significant biases. While current IPC correction methods are prohibitively slow for a per-pixel application, our new method uses separate measurements of the IPC kernel to calculate the gain almost instantaneously. Using test data from a flight detector of the ESA Euclid mission, the IPC correction recovers the results of slower methods with 0.1% accuracy. The nonlinearity correction ensures that the estimated gain is independent of signal, correcting a bias of more than 2.5%.
The International Geomagnetic Reference Field (IGRF) model is a series of models that describe the large scale magnetic field measured at the Earth’s surface. It is used by a wide range of scientists and industries, including in navigation, space weather applications, and resource exploration. The 14th generation, IGRF-14, is the result of an international collaboration over 19 different lead research groups. This new generation provides a definitive model of the main magnetic field (MF) for the epoch 2020.0, a prediction of the MF for 2025.0, and a predicted average annual time variation of the magnetic field for 2025.0 - 2030.0. The first time derivative of the magnetic field, known as secular variation, (SV) is linked to the flow at the top of Earth’s outer core. As such, the ensemble of IGRF-14 candidate models can be used to investigate predicted core flow variability between 2020.0 and 2030.0. We use the pygeodyn Python package using the AR-1 ‘dense’ methodology, the 71
Considering scattering in radiative transfer calculations often leads to extensively long computation times that can be prohibitive, especially in the operational context of satellite missions. Over time, numerous methods were developed to accelerate scattering calculations. In this paper, based and further built upon the work of O'Dell [1], we describe the implementation of the Low-Stream Interpolation acceleration technique in the 4A/OP radiative transfer model. The method's acceleration relies on the execution of computationally expensive calculations only for representative points, which represent the regions in the gas absorption optical depth space called "bins". For all other points the calculation is performed at a low accuracy and by subsequent interpolation. We have considered a number of method's aspects, and introduced various modifications in order to optimise its accuracy and computation time. This includes: a) an extension of the method to Jacobians, b) modifications of bin and sub-bin divisions, c) implementation of automatic binning and its comparison to fixed bins, d) improvement of the computation of representative points, e) improvement of the definition of "significant scattering" used by the method, f) avoiding the redundancy of high-accuracy computation at large gas absorption optical depths, g) optimisations of the method computation domain size and h) evaluations of various possible accelerations of low-accuracy calculations. We applied the method on the MicroCarb O2 and CO2 bands in nearinfrared and shortwave-infrared over a large variety of geophysical cases and discussed the impacts of the modifications and the overall performance. We confirmed that the Low-Stream Interpolation is a powerful technique to accelerate the scattering calculations and, in our model, it provided relative accuracies on polarised and unpolarised radiances and Jacobians lower than 0.05 % with acceleration of 10-50 times.
Miniaturization and cost reduction have been identified by CNES as essential assets to enable ground-braking scientific observatories and support future exploration of the Moon, Mars and small bodies. A new generation of scientific instruments is being developed aiming at a format between fractions of 1 kg to a few kg. These instruments will be available for small surface missions, static or mobile, but they are also applicable to larger infrastructures, or can be included in the investigation tool set of astronauts. We will elaborate on these new miniaturized versions, which encompass: •Compact visible and Short Wavelength Infrared Cameras based on advanced imaging technologies •MicroLIBS (Laser Induced Breakdown Spectroscopy) •Microchip gas chromatographic columns •Ground penetrating radars •Compact seismometers based on geophone sensors •Dosimeters and spectrometers for protons and electrons
