The Small Satellite-Based, Imaging X-Ray Polarimeter Explorer (IXPE) Mission

The Imaging X-ray Polarimeter Explorer (IXPE) focuses on high energy astrophysics in the 2—8 keV x-ray band. IXPE is designed to explore general relativistic and quantum physics effects of gravity, energy, electric and magnetic fields at extreme limits. IXPE, a NASA Small Explorer (SMEX) Mission, will add new dimensions to on-orbit x-ray science: polarization degree, polarization angle and extended object polarization imaging. Polarization uniquely probes physical anisotropies that are not otherwise measurable—ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin. Detailed imaging enables the specific properties of extended x-ray sources to be differentiated. The IXPE Observatory consists of spacecraft and payload modules built up in parallel to form the Observatory during system integration and test. The payload includes three polarization-sensitive, x-ray detector arrays paired with three x-ray mirror module assemblies (MMA). A deployable boom provides the correct separation (focal length) between the detector units and MMAs. Currently, the boom has been delivered, all four detectors units (DU) are complete, the detectors service unit (DSU) is complete, instrument system testing has been completed (DSU with 3 DUs), three of four MMAs is built and all spacecraft components except the solar array have been delivered along with the spacecraft and payload structures. Payload and spacecraft integration and test (I&T) started in March 2020. This paper overviews the flight segment (the Observatory, payload, and spacecraft implementation concepts) with emphasis on the build status and summarizes the launch segment. Launch is planned to occur on a Falcon 9 launch vehicle during Summer 2021. The paper summarizes the impacts of switching from the ‘design-to baseline’ of Pegasus XL to the selected launch vehicle for flight, Falcon 9. COVID-19 impacts to the Project are also summarized. The paper will close with a summary of the mission development status. The Project is firmly into the build phase for both the spacecraft and payload and rapidly approaching Observatory I&T

Effet d'une crise dystrophique dans l'etang de Salses-Leucate

The dystrophic crisis in the lagoon of Salses-Leucae in 1979-1980 resulted in a bloom of the chlorophyceae Nannochloris sp. which attained a density in the order of 10 super(9) cells/litre. The worst effect was the destruction of oyster and mussel cultures because of overfeeding. This bloom also caused high turbidity which induced the destruction of large parts of sea-grass communities (Zostera)). One year after the beginning of this crisis, a gradual improvement of ecological conditions was noted, especially in the pelagic zone. The benthic environment recovered at a much slower rate. Sea-grass showed signs of recovery, organic matter concentrations and bacterial populations decreased. Furthermore, the macrofauna density increased notably. Nevertheless, the situation remained precarious, for in October, concentrations of organic matter and sulfate-reducing bacteria were still high in sediments. The considerable phytoplanktonic development exists because of large amounts of mineral elements, probably untreated sewage

Imaging X-ray Polarimetry Explorer: Prelaunch

Launched on 2021 December 9, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer Mission in collaboration with the Italian Space Agency (ASI). The mission will open a new window of investigation—imaging x-ray polarimetry. The observatory features three identical telescopes, each consisting of a mirror module assembly with a polarization-sensitive imaging x-ray detector at the focus. A coilable boom, deployed on orbit, provides the necessary 4-m focal length. The observatory utilizes a three-axis-stabilized spacecraft, which provides services such as power, attitude determination and control, commanding, and telemetry to the ground. During its 2-year baseline mission, IXPE will conduct precise polarimetry for samples of multiple categories of x-ray sources, with follow-on observations of selected targets

The Imaging X-Ray Polarimetry Explorer (IXPE): technical overview IV

Scheduled to launch in late 2021 the Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer Mission designed to open up a new window of investigation -- X-ray polarimetry. The IXPE observatory features 3 identical telescope each consisting of a mirror module assembly with a polarization-sensitive imaging x-ray detector at its focus. An extending beam, deployed on orbit provides the necessary 4 m focal length. The payload sits atop a 3-axis stabilized spacecraft which among other things provides power, attitude determination and control, commanding, and telemetry to the ground. During its 2-year baseline mission, IXPE will conduct precise polarimetry for samples of multiple categories of x-ray sources, with follow-on observations of selected targets. IXPE is a partnership between NASA and the Italian Space Agency (ASI)

The Imaging X-Ray Polarimetry Explorer (IXPE): Pre-Launch

International audienceLaunched on 2021 December 9, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer Mission in collaboration with the Italian Space Agency (ASI). The mission will open a new window of investigation—imaging x-ray polarimetry. The observatory features three identical telescopes, each consisting of a mirror module assembly with a polarization-sensitive imaging x-ray detector at the focus. A coilable boom, deployed on orbit, provides the necessary 4-m focal length. The observatory utilizes a three-axis-stabilized spacecraft, which provides services such as power, attitude determination and control, commanding, and telemetry to the ground. During its 2-year baseline mission, IXPE will conduct precise polarimetry for samples of multiple categories of x-ray sources, with follow-on observations of selected targets