The Imaging X-Ray Polarimeter Explorer (IXPE) Mission System Using a Small Satellite

The goal of the Imaging X-Ray Polarimeter Explorer (IXPE) Mission is to expand understanding of high-energy astrophysical processes and sources. IXPE will add two new dimensions to on-orbit x-ray science: polarization measurements and detailed 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. MSFC provides the X-ray optics and Science Operations Center (SOC) along with mission management and systems engineering. Ball is responsible for the spacecraft, payload mechanical elements and flight metrology system and payload, spacecraft and system I&T along with launch and operations. The MOC is located at CU/LASP. IAPS/INAF and INFN provide the polarization-sensitive detector units (DU) and detectors service unit (DSU) via the Italian Space Agency (ASI). The Observatory communicates with the ASI-contributed Malindi ground station via S-band link. The science team generates and archives IXPE data products at the HEASARC. The IXPE “mission system” is made up of the flight segment, ground segment and launch segment – this paper briefly summarizes the IXPE mission science objectives, overviews the flight segment (the payload, spacecraft, and Observatory implementation concepts), and summarizes the expected operations concept. A SpaceX Falcon 9 launch vehicle was selected in June 2019 to launch the IXPE Observatory. Mission CDR occurred in June 2019 and the IXPE Project is now firmly in the build phase

Small Satellite Platform Imaging X-Ray Polarimetry Explorer (IXPE) Mission Concept and Implementation

Scientists and astronomers world—wide have a great interest in exploring the hidden details of some of the most extreme and exotic astronomical objects, such as stellar and supermassive black holes, neutron stars and pulsars. However, one cannot directly image what’s going on near objects like black holes and neutron stars, but studying the polarization of X-rays emitted from their surrounding environments reveals the physics of these enigmatic objects. The goal of the Imaging X-Ray Polarimetry Explorer (IXPE) Mission is to expand understanding of high-energy astrophysical processes and sources, in support of NASA’s first science objective in Astrophysics: “Discover how the universe works.” Polarization uniquely probes physical anisotropies—ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin—that are not otherwise measurable. X-ray polarimetry is the focus of the IXPE science mission. 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, each paired with its corresponding grazing angle incidence mirror module assemblies (MMA). A deployable boom provides the correct separation (focal length) between the detector units (DU) and MMAs. These Payload elements are supported by the IXPE Spacecraft which is derived from the BCP-100 small Spacecraft architecture. A star tracker is a key element of the attitude determination and control system. It is mounted directly with the Payload to minimize alignment errors between the spacecraft and payload. This paper summarizes the IXPE mission science objectives and describes the Observatory implementation concept including the payload and spacecraft elements

Imaging X-Ray Polarimetry Explorer Mission Attitude Determination and Control Concept

The goal of the Imaging X-Ray Polarimetry Explorer (IXPE) Mission is to expand understanding of high-energy astrophysical processes and sources, in support of NASA's first science objective in Astrophysics: "Discover how the universe works." X-ray polarimetry is the focus of the IXPE science mission. Polarimetry uniquely probes physical anisotropies-ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin-that are not otherwise measurable. The IXPE Observatory consists of Spacecraft and Payload modules. The Payload includes three polarization sensitive, X-ray detector units (DU), each paired with its corresponding grazing incidence mirror module assemblies (MMA). A deployable boom provides the correct separation (focal length) between the DUs and MMAs. These Payload elements are supported by the IXPE Spacecraft. A star tracker is mounted directly with the deployed Payload to minimize alignment errors between the star tracker line of sight (LoS) and Payload LoS. Stringent pointing requirements coupled with a flexible structure and a non-collocated attitude sensor-actuator configuration requires a thorough analysis of control-structure interactions. A non-minimum phase notch filter supports robust control loop stability margins. This paper summarizes the IXPE mission science objectives and Observatory concepts, and then it describes IXPE attitude determination and control implementation. IXPE LoS pointing accuracy, control loop stability, and angular momentum management are discussed

The Imaging X-ray Polarimetry Explorer (IXPE): Technical Overview

The Imaging X-ray Polarimetry Explorer (IXPE) will expand the information space for study of cosmic sources, by adding linear polarization to the properties (time, energy, and position) observed in x-ray astronomy. Selected in 2017 January as a NASA Astrophysics Small Explorer (SMEX) mission, IXPE will be launched into an equatorial orbit in 2021. The IXPE mission will provide scientifically meaningful measurements of the x-ray polarization of a few dozen sources in the 2-8 keV band, including polarization maps of several x-ray-bright extended sources and phase-resolved polarimetry of many bright pulsating x-ray sources

The Imaging X-Ray Polarimetry Explorer (IXPE): Technical Overview II

The Imaging X-ray Polarimetry Explorer (IXPE) will add polarization to the properties (time, energy, and position) observed in x-ray astronomy. A NASA Astrophysics Small Explorer (SMEX) in partnership with the Italian Space Agency (ASI), IXPE will measure the 28-keV polarization of a few dozen sources during the first 2 years following its 2021 launch. The IXPE Observatory includes three identical x-ray telescopes, each comprising a 4-m-focal-length (grazingincidence) mirror module assembly (MMA) and a polarization-sensitive (imaging) detector unit (DU), separated by a deployable optical bench. The Observatorys Spacecraft provides typical subsystems (mechanical, structural, thermal, power, electrical, telecommunications, etc.), an attitude determination and control subsystem for 3-axis stabilized pointing, and a command and data handling subsystem communicating with the science instrument and the Spacecraft subsystems

The Imaging X-ray Polarimetry Explorer (IXPE): technical overview III

IXPE, the Imaging X-ray Polarimetry Explorer, is a NASA SMEX mission with an important contribution of ASI that will be launched with a Falcon 9 in 2021 and will reopen the window of X-ray polarimetry after more than 40 years. The payload features three identical telescopes each one hosting one light-weight X-ray mirror fabricated by MSFC and one detector unit with its in-orbit calibration system and the Gas Pixel Detector sensitive to imaging X-ray polarization fabricated by INAF/IAPS, INFN and OHB Italy. The focal length after boom deployment from ATK-Orbital is 4 m, while the spacecraft is being fabricated by Ball Aerospace. The sensitivity will be better than 5.5% in 300 ks for a 1E-11 erg/s/cm2 (half mCrab) in the energy band of 2-8 keV allowing for sensitive polarimetry of extended and point-like X-ray sources. The focal plane instrument is completed, calibrated and it is going to be delivered at MSFC. We will present the status of the mission at about one year from the launch

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