The Imaging X-Ray Polarimetry Explorer (IXPE) is designed 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 measurements and imaging are key capabilities of the IXPE observatory. IXPE, an international collaboration between NASA and the Italian Space Agency (ASI), is a NASA Small Explorer designed as a 2-year mission. It launches to a circular LEO orbit at an altitude of 600 km and an inclination of ~0 degrees on a Falcon 9 launch vehicle. The payload uses a single science operational mode to capture the X-ray data from the science targets. The mission design follows a simple observing paradigm: pointed viewing of known X-ray sources (with known locations in the sky) over multiple orbits (not necessarily consecutive orbits) until the observation is complete. IXPE's payload is a set of three identical, imaging, X-ray polarimetry telescopes mounted on a common optical bench and co-aligned with the pointing axis of the spacecraft. The BCP-Small spacecraft provides the necessary resources to support and operate the payload elements and enable continuous science data collection. The Observatory communicates with ground stations via S-band link. The ground system consists of three major elements: the ground stations for data receipt and command upload to the Observatory; the Mission Operation Center (MOC); and Science Operations Center (SOC). Launch occurred on 9 December 2021. The IXPE Observatory has been collecting science data from cosmic X-ray sources since 11 January 2022. These include extreme astronomical objects, such as stellar-mass and supermassive black holes, magnetars, Blazars, neutron stars, and pulsars. This paper summarizes the IXPE mission, describes the Observatory, ground system, and commissioning and overviews recent science results.

Scheduled to launch in late 2021, 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 3 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 3-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 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 onorbit 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 polarizationsensitive, 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.

Ball Aerospace has been conducting detailed studies on the feasibility of accommodating chemical (including green) propulsion and solar electric propulsion (SEP) on small Ball Configurable Platform (BCP), ESPA-class spacecraft. The BCP-Small spacecraft bus is used as the baseline to leverage its flight heritage (STPSat-2, STPSat-3, GPIM (in storage, awaiting launch) and IXPE (under development). The study approach is focused on aligning the BCP-Small design with multiple ongoing and upcoming small sat pursuits. Work is focusing on Demonstration-Class and Operational-Class spacecraft product development with reduced recurring engineering, volume production capability and equivalent or improved capabilities. Propulsion module options are considered for both BCP-Small products. Chemical systems providing up to 100's of m/s AV and SEP providing up to 1000's of m/s AV are being assessed. Chemical systems being assessed include hydrazine-based systems and green propellant systems based on the propellants AF-M315E and LMP-1035. SEP systems include several different plasma thruster systems including Hall and ion. This work is making use of the improved mass qualification limits for ESPA, the newly defined ESPA-Heavy and ESPA-Grande. Mission applications in various Earth orbits are the current focus for propulsion-enabled, BCP-Small spacecraft. The results of the ongoing work show BCP-Small spacecraft can be modified to accommodate meaningful chemical propulsion or SEP capability while meeting the mass and volume constraints for ESPA and/or ESPA-Grande. Mission options starting in both GTO and LEO are included in the assessments. This paper further summarizes the BCP-Small spacecraft design and capabilities, status of the heritage flight and in-development programs and describes how the BCP-Small is adapted to include chemical or SEP along with on-orbit control.

When the Imaging X-ray Polarimetry Explorer (IXPE) launches in 2021, the world will have a new orbiting Xray observatory capable of examining previously unexplored celestial phenomena. For the first time, an earth-orbiting observatory will be able to resolve the polarization angle of each incoming X-ray photon in an imaged scene, and provide polarization measurements of each source within the instrument's field of view. The two top-level project requirements that drive the mission design and observatory capability are the execution, in a one year period, of a Design Reference Mission (DRM) containing 48 representative targets, and the ability to observe any location on the celestial sphere for 30 days every six months. IXPE exceeds these driving requirements with a straightforward observatory design concept that allows a large instrument field of regard with a fixed solar array. IXPE completed its preliminary design review in June 2018 with a baseline power and thermal design that accommodates all observatory attitudes that maintain a +/- 25 degree angle between the body-fixed solar array and the plane normal to the sun vector. This paper examines how observatory attitude affects power consumption, how the DRM targets drive the observatory power and thermal design, and potential system design trades.

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 astrophysical anisotropies-ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin-that are not otherwise measurable. IXPE will conduct X-ray polarimetry for multiple categories of cosmic X-ray sources that are likely to be polarized such as neutron stars, stellar-mass black holes, supernova remnants and active galactic nuclei. 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 polarizationsensitive, X-ray detectors, each paired with its corresponding grazing incidence mirror module assembly (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. This paper summarizes the IXPE mission science objectives, describes the Observatory implementation concept including the payload and spacecraft elements and summarizes the expected concept of operations.

Ball Aerospace has studied the Solar Electric Propulsion (SEP) implementation for the past 20 years. Work has included concept development for ARM, SEP demonstration mission options, modular SEP tug definition, launch vehicle SEP-based upper stages, ESPA-class SEP-Sat configurations, micro-impulse science craft precise positioning, micro-impulse formation flying and focused interplanetary spacecraft designs for high AV, typically outer planet and small body, science missions. Ball has looked at pulsed and continuous thrust SEP implementations, systems ranging from watts to tens of kilowatts, RN of thrust at 8,000 s specific impulse to tens of newtons of thrust at 2500 s specific impulse. There have been numerous improvements in EP and power generation technologies over the past 5 years. The realization of the MegaFlex and MegaRosa solar arrays and flight demo of MegaRosa are key on the power side. Micro-thruster development and Hall thruster system development at both high power and low power are enabling. Ball continues to examine SEP options for mission applications on Ball Configurable Platforms (BCP) in light of these new developments. Mission applications in various Earth orbits and interplanetary space are considered. This paper summarizes recent Ball SEP activities in the areas of SEP tug concepts, SEP demonstration mission, outer planet science missions and EELV Secondary Payload Adapter (ESPA)-class SEPSats. Ongoing work focuses on ESPA-class, SEPSat capabilities definition and SEP accommodation on small BCP platforms. Mission options starting in both LEO and GTO were explored with multiple thruster system types. BCP ESPA-class, SEPSats with the highest Isp system (ion) can escape from Earth's gravity, in some cases with sufficient C3 to go to Venus or Mars.

Ball Aerospace & Technologies Corp. (Ball) has conceptually developed a modular, reusable Solar Electric Propulsion (SEP) Tug that leverages heritage, commercial capabilities in spacecraft buses and electric propulsion (EP) to minimize the time and cost to market. The SEP Tug is a stand-alone, scalable, modular vehicle which combines a Mission Module based on commercially available spacecraft bus element from Ball, a SEP Module using high power electric propulsion, an Reaction Control System (RCS) Module based on monopropellant hydrazine (a green monopropellant option is under consideration) and a Payload Module/payload accommodation platform. SEP Module designs have examined implementation of both ion engine and Hall thruster systems and utilizes flexible blanket arrays. An optional Xenon Tank Module is available to accommodate larger propellant requirements. This modular architecture can satisfy the needs of the Asteroid Redirect Vehicle (ARV) and a broad array of customers and markets including: servicing, resupply, replenishment, payload delivery, operational orbit change and debris removal operations. The SEP Tug provides a reusable platform for industry to leverage for multiple mission needs while DOD benefits can include constellation resiliency.

The Falco orbital debris removal mission is a concept devised to provide a credible solution to removing a large piece of orbital debris from space for a reasonable mission cost. The target orbital debris for the mission is the defunct Infrared Astronomical Satellite (IRAS) telescope, which was chosen because it won't deorbit on its own, and because Ball Aerospace built it and so knows the details of the vehicle. The overall mission concept is very straightforward, except for the passive despin device that is used to simplify capture of the spinning spacecraft. The passive despin device is a novel method of reducing the spin rate of the orbital debris using the Earth's magnetic field, and helps to simplify the guidance, navigation, and control aspects of capturing a spinning piece of orbital debris. This paper will provide an overview of the mission, with a focus on the passive despin device and the simplifications it provides to the overall system.

The trajectory design for the Dark Ages Radio Explorer (DARE) mission con-cept involves launching the DARE spacecraft into a geosynchronous transfer orbit (GTO) as a secondary payload. From GTO, the spacecraft then transfers to a lunar orbit that is stable (i.e., no station-keeping maneuvers are required with minimum perilune altitude always above 40 km) and allows for more than 1,000 cumulative hours for science measurements in the radio-quiet region located on the lunar farside.

Ball Aerospace & Technologies Corp participated in a Space Act Agreement with NASA GRC to determine the feasibility of accommodating enough Solar Electric Propulsion (SEP) on the Ball ESPA-class bus to result in a mission of interest to Ball customers. The baseline for the study was the ESPA-class BCP-100 bus. Since the BCP-100 bus has flight heritage on USAF programs, the approach for the study was to use the existing bus design and minimize changes to only those necessary to accommodate the SEP system. This approach maintains high heritage and minimizes the amount of Non-Recurring Engineering required for the bus. High heritage components were also selected for the SEP system when available, including an off-the-shelf Xenon tank, existing cathode, HET thruster and Xenon feed control, allowing future development funding to be focused on a PPU compatible with the existing BCP-100 28 V power bus. The results of the study show that while meeting the ESPA envelope and mass requirements, the BCP-100 can accommodate enough SEP capability to allow the orbit to be raised or lowered anywhere within LEO or change the inclination up to 10° from a LEO starting point. From a GTO starting point, an elliptical orbit with apogee at GEO is also possible.

Ball Aerospace & Technologies Corp. participated in a Space Act Agreement with NASA GRC to determine the feasibility of accommodating Solar Electric Propulsion (SEP) on an ESPA-class spacecraft. The BCP-100 bus was used as the baseline to leverage its flight heritage (STPSat-2 and STPSat-3, with GPIM under development). The study approach focused on minimizing changes to the existing bus design by modifying only what was necessary to accommodate the SEP system (structures, thermal and harnessing). This approach maintains high heritage and minimizes the amount of non-recurring engineering required for the bus. High heritage components are also selected for the 200 W SEP system including an off-the-shelf xenon tank, Hall effect thruster and cathode, and xenon feed control, allowing future development funding to be focused on a PPU compatible with the existing BCP-100 low voltage (28 V) power bus. The results of the study show a BCP-100 can be modified to accommodate meaningful SEP capability while meeting the mass and volume constraints for an ESPA launch. The Hall thruster SEP system produces similar to 1500 m/s Delta V with 20 kg of xenon propellant. This paper summarizes the BCP-100 design and capabilities, status of the heritage flight and in-development programs and summarizes how the BCP-100 is adapted to include SEP. Mission options starting in both LEO and GTO were explored and are discussed.

The SEPTD mission is a stepping stone leading to a reusable electric propulsion stage by demonstrating transfers from LEO to GEO and back to LEO. This set of high V trajectories demonstrates long-term SEP operations and flies the SEPTD space vehicle through the radiation belts, sustained plasma environments, diverse distributed inertia Space Vehicle control environments and repeated Space Vehicle occultations. A large number of trades cases and point designs have been analyzed for requirements development, system sizing, and concept of operations definition. The trades and point designs have been completed using various methods and tools at ranging levels of fidelity. The focus was to find high V solutions that fit within the budget (and hence mass) constraints of the SEPTD Mission requirements. Mass is purposefully constrained to constrain cost. The Baseline Mission begins in LEO, performs a low-thrust transit to GEO, transits back down to an equatorial LEO orbit, and then optionally spirals out from LEO to L1. There are a wide range of mission variants including EP system selection, and the Baseline Mission provides the performance capability for flexibility; including extended missions to NEOs, low lunar orbit, or the moons of Mars.

Ball Aerospace has provided hardware for many missions in deep space including the complete flight systems for the highly successful Deep Impact Mission and the soon to be launched Kepler planet finding mission. Deep space instruments include the HiRISE camera at Mars, the Ralph camera for New Horizons (on its way to Pluto), the two Spitzer instruments and the telescope, and the telescope for the upcoming James Webb Space Telescope (JWST) observatory. Ball continues to work towards future deep space mission opportunities. This paper describes our deep space mission spacecraft bus work (Micromissions and Starlight mission concept architectures, and the Deep Impact and Kepler mission architectures), earth remote sensing bus background and discusses Ball Aerospace spacecraft architecture directions in light of these concepts and missions. We cover our mission design work to support deep space missions.