Mission Concept for Demonstrating Small-Spacecraft True Anomaly Estimation Using Millisecond X-Ray Pulsars

Navigation based on X-ray pulsars was first suggested in 1981 for deep space navigation as an alternative to the conventional Deep Space Network (DSN) which is inaccurate at large distances from the Earth. This idea was recently demonstrated using the NICER/SEXTANT instrument onboard the ISS. X-ray pulsar-based navigation is of of great interest as it eliminates the reliance on Earth-based systems, and is yet to be implemented as an autonomous navigation system for deep space missions. For the purpose of navigation, X-ray millisecond pulsars are the most appropriate celestial sources. They emit unique, stable and periodic radiation that exhibits high timing stability comparable to atomic clocks, thus making them suitable as navigational beacons. The phase difference between the pulsar’s pulse profile obtained at the satellite and a reference profile is tied to the position of the satellite with respect to the chosen reference location, typically considered to be the Solar System Barycenter (SSB). Measurements from at least four pulsars are required to estimate the 3D position, velocity, and time of the satellite. This article describes a small satellite mission concept being developed at the Small-spacecraft Systems and PAyload CEntre (SSPACE) at the Indian Institute of Space Science and Technology (IIST) that aims to demonstrate navigation in space using X-ray millisecond pulsars. The satellite contains a miniaturized X-ray timing detector payload, which extracts accurate pulse profiles from detected pulsar signals. A mission-specific algorithm is developed that uses measurements from a single pulsar to estimate only the true anomaly of the satellite, since given the orbital insertion, the other orbital elements are assumed to be stationary. Additionally, the process of pulsar selection is presented, where pulsars are ranked according to the weighted parameters of stable time periods, visibility from the chosen orbital configuration, and high signal-to-noise ratio with respect to the diffuse X-ray background. This is followed by details of the instrument design and concept of operations of this technology demonstration mission. The article concludes with an overview of the systems architecture of the small-satellite, which has a standard 6U CubeSat form factor and details regarding the various subsystems including the On Board Computer, Electrical Power System, Communication system, and Attitude Determination and Control System are discussed. A successful demonstration of this mission will pave the way for future small-satellite missions, where 3D position estimation can be carried out using multiple X-ray pulsar detectors

Design and Development of a PS4-OP Payload for Solar Spectral Irradiance Measurements and Technology Demonstration of Small-Satellite Subsystems

This article describes the design and development of INSPIRE-0, a payload on the spent stage of the ISROs PSLV. Recently, the Indian Space Research Organisation (ISRO) released an announcement of opportunity inviting proposals to develop payloads that can be tested on the PS4-Orbital Platform (PS4-OP). This platform is a novel idea formulated by ISRO to use the spent fourth/final stage of the Polar Satellite Launch Vehicle (PSLV), called the PS4, to conduct in-orbit scientific experiments and technology demonstration of small-satellite subsystems. INSPIRE-0 is a PS4-OP payload, jointly developed by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder, the Indian Institute of Space Science and Technology (IIST), and the Nanyang Technological University (NTU) in Singapore. This payload has two main objectives. Firstly, the scientific objective is to characterize the solar spectrum using a novel sensor, developed by NTU, that has a wide frequency range from visible to near the infra-red region. The specific objective of the INSPIRE-0 payload is to demonstrate that accurate Solar Spectral Irradiance (SSI) continuous measurements are possible using new compact and robust disruptive technologies. A successful demonstration will pave the way for a future constellation of CubeSats that will provide a very cost-effective way to monitor the Total Solar Irradiance and SSI of the sun in the various spectral bands. Secondly, the INSPIRE-0 payload aims to flight qualify the in-house developed subsystems for the INSPIRESat-1 small satellite mission, namely, the Command and Data Handling (C&DH) Subsystem and the Electrical Power Subsystem (EPS). The article first describes the systems architecture of the payload which has a size of 15cm x 10cm x 7.5 cm, a mass of 1kg, and power consumption of 1.75 W. This is followed by the details of the science instrument and an overview of the different subsystems, namely the C&DH, the EPS, and the PS4-OP interface board. The article concludes with the details of the testing, including comprehensive performance tests and environmental tests, performed to prepare the payload for a planned launch on the PS4-OP in the third quarter of 2021

Development of a Power-Efficient, Low Cost, and Flash FPGA Based On-Board Computer for Small-Satellites

On-Board Computers (OBCs) for Small-satellite missions are typically required to be designed using industrial grade Commercial-of-the-shelf (COTS) components due to budget constraints and short mission duration. The OBC must provide a variety of interfaces due to the diverse nature of COTS subsystems having different interface definitions. Traditional OBC designs with standard microcontrollers have fixed interfaces that require modification of the motherboard circuit/layout when the external interfaces require changes. Thus, a possible solution is to have an FPGA in-addition to the micro-controller thereby providing a configurable interface capability. System-on-Chip (SoC) devices that integrate a microcontroller with FPGA fabric provide an ideal solution for reducing the development time. Additionally, the limited availability of power in small satellite missions makes it essential to use power-efficient devices. Furthermore, single event upsets (SEUs) and single event latch-up (SELs) are a major problem for OBCs designed for Low Earth Orbit (LEO) small-satellite missions. Flash memory-based FPGAs provide the benefit of low power consumption and they are more also fault-tolerant due to their intrinsic robustness against induced single event upsets compared to SRAM-based FPGAs. This article describes the OBC developed using the flash-based Microsemi SmartFusion2 SoC FPGA as its key component, for the INSPIRESat-1 and INSPIRESat-2 small-satellite missions. The OBC is designed in two form factors one with 13cm x 10cm dimensions for INSPIRESat-1 and the other with 10cm x 10cm dimensions for INSPIRESat-2. The OBC uses a COTS System-on-Module (SoM) developed by Emcraft containing the SmartFusion2 SoC, which is mounted on a custom-designed motherboard containing other peripherals including flash memory, SD Cards, and an external watchdog timer. The OBC has a total power consumption of approximately 1 W, in the final flight configuration. The article here describes the architecture of the OBC in detail, the key features of which include multiple on-board memories, a multi-level reset methodology, and reconfigurable input/output interfaces. The article concludes with the details of comprehensive performance tests conducted on the INSPIRESat-1 OBC, which has qualified TRL-8 (technology readiness level) status after completing required environmental tests such as the Thermal Vacuum Test (TVAC) and vibration test as a part of the integrated satellite. INSPIRESat-2 was launched in January 2021 and due to the successful working of the OBC in fight it has achieved TRL-9 status through this mission. The OBC developed for INSPIRESat-1 is planned to achieve TRL-9 status after its launch in the third quarter of 2021

INSPIRESat-1: A Year of On-Orbit Operations

INSPIRESat-1 (IS-1) was the first mission under the INternational Satellite Program In Research and Education (INSPIRE) program, a consortium of universities coming together to space science missions. IS-1 launched on February 14, 2022 at 00:30 UTC to a sun synchronous dawn-dusk orbit onboard the Indian Space Research Organization\u27s PSLV C52 mission. The IS-1 spacecraft was primarily developed at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado with significant contributions from the Indian Institute of Space Science and Technology (IIST), NCU of Taiwan and Nanyang Technological University (NTU) in Singapore. The IS-1 carries two scientific instruments: The Compact Ionospheric Probe (CIP) developed at National Central University (NCU) for studying Earth\u27s dynamic ionosphere and the NASA funded Dual-zone Aperture X-ray Solar Spectrometer (DAXSS) developed at LASP for studying the highly-variable solar X-ray radiation. DAXSS is a follow on from the highly successful MinXSS 1 &2 missions. First contact was established with the spacecraft 45 minutes after launch. The first science instruments were turned on by February 27th. DAXSS has now observed multiple solar flares in the current increasing phase of solar cycle 25 for a period of 16 months. In this paper we will present details on spacecraft performance in a unique dawn dusk orbit which presents thermal challenges not encountered frequently by nano-satellite platforms. We also present preliminary science results from CIP and DAXSS instruments from a year of on-orbit operations. Operations of the Spacecraft has also been unique with multiple universities commanding and downlinking science data

IDEASSat: The Ionosphere Dynamics Explorer and Attitude Subsystem Satellite

CubeSats are becoming an increasingly important and viable platform for space physics observations, in addition to their longstanding role in education and technology demonstration. With proper mission formulation, design, and testing, CubeSats have the potential to extend the capability of observations from large satellite missions. The Ionosphere Dynamics Explorer and Attitude Subsystem Satellite (IDEASSat / INSPIRESat-2) is a 3U CubeSat mission funded in part by the Taiwan National Space Organization (NSPO) and executed by Taiwan National Central University (NCU) in conjunction with international partners as part of the International Satellite Program in Research and Education (INSPIRE) consortium. The science payload is the Compact Ionospheric Probe (CIP): an all in one insitu plasma sensor combining retarding potential analyzer, ion trap, ion drift meter, and planar Langmuir probe modes in a time-sharing manner, providing measurements of ion density, temperature, composition, and drift velocity, as well as electron temperature. CIP traces its heritage to the Advanced Ionospheric Probe (AIP) launched and currently operational onboard the FORMOSAT-5 satellite since August 2017. With both spacecraft operational in high inclination Sun synchronous orbits following the expected IDEASSat launch in 2020, comprehensive in-situ measurements of ionospheric variability and irregularities can be obtained to understand their effects on radio communications and satellite navigation signals

A Very Low Altitude Satellite for Equatorial Ionosphere and Atmospheric Temperature Measurements

The Satellite Research Centre at Nanyang Technological University is currently developing the Atmospheric Coupling and Dynamics Explorer (ARCADE) Mission, which is flying a hall effect thruster to progressively lower the altitude from an initial 500 km to 250 km. ARCADE is also the fourth satellite in the INSPIRE (International Satellite Program in Research and Education) satellite series with joint development from IIST, India and NCU, Taiwan. ARCADE is a 27U spacecraft carrying an ionospheric plasma payload which will make ion temperature, velocity, density and electron temperature measurements. The satellite will be launched along with six other Singaporean satellites on a Singapore dedicated PSLV in 2020 into a near equatorial orbit. Since the final altitude is expected to be 250 km, the ARCADE/INSPIRESat-4 mission provides an excellent opportunity to study the equatorial ionosphere at low altitudes where the ion and electron density are much higher. The mission is expected to provide new information on plasma irregularities along the magnetic equator. The mission is also a technology demonstration of a hall effect thruster developed by French Startup \u27Thrust Me\u27. Another addition to the mission is a Spatial Heterodyne Interferometer Infra-Red Imager for imaging the Mesosphere and Lower thermosphere region between 60-120 km. The SHI instrument will provide temperature information and help for understanding the dynamics of the equatorial MLT region. The presentation will cover the teams approaches to dealing with Very Low Earth Orbit (VLEO) and the challenges it poses in terms of thermal and atomic oxygen effects