A novel astronomical application for formation flying small satellites

OLFAR, Orbiting Low Frequency Antennas for Radio Astronomy, will be a space mission to observe the universe frequencies below 30 MHz, as it was never done before with an orbiting telescope. Because of the ionospheric scintillations below 30 MHz and the opaqueness of the ionosphere below 15 MHz, a space mission is the only opportunity for this as yet unexplored frequency range in radio astronomy. The frequency band is scientifically very interesting for exploring the early cosmos at high hydrogen redshifts, the so-called dark-ages and the epoch of reionization, the discovery of planetary and solar bursts in other solar systems, for obtaining a tomographic view of space weather, ultra-high energy cosmic rays and for many other astronomical areas of interest. Because of the low observing frequency the aperture size of the instrument must be in the order of 100 km. This requires a distributed space mission which is proposed to be implemented using formation flying of small satellites. The individual satellites are broken down in five major subsystems: the spacecraft bus, the antenna design, the frontend, backend and data transport. One of the largest challenges is the inter-satellite communication. In this paper the concept and design considerations of OLFAR are presented

National Security Space Launch

The United States Space Force’s National Security Space Launch (NSSL) program, formerly known as the Evolved Expendable Launch Vehicle (EELV) program, was first established in 1994 by President William J. Clinton’s National Space Transportation Policy. The policy assigned the responsibility for expendable launch vehicles to the Department of Defense (DoD), with the goals of lowering launch costs and ensuring national security access to space. As such, the United States Air Force Space and Missile Systems Center (SMC) started the EELV program to acquire more affordable and reliable launch capability for valuable U.S. military satellites, such as national reconnaissance satellites that cost billions per satellite. In March 2019, the program name was changed from EELV to NSSL, which reflected several important features: 1.) The emphasis on “assured access to space,” 2.) transition from the Russian-made RD-180 rocket engine used on the Atlas V to a US-sourced engine (now scheduled to be complete by 2022), 3.) adaptation to manifest changes (such as enabling satellite swaps and return of manifest to normal operations both within 12 months of a need or an anomaly), and 4.) potential use of reusable launch vehicles. As of August 2019, Blue Origin, Northrop Grumman Innovation Systems, SpaceX, and United Launch Alliance (ULA) have all submitted proposals. From these, the U.S. Air Force will be selecting two companies to fulfill approximately 34 launches over a period of five years, beginning in 2022. This paper will therefore first examine the objectives for the NSSL as presented in the 2017 National Security Strategy, Fiscal Year 2019, Fiscal Year 2020, and Fiscal Year 2021 National Defense Authorization Acts (NDAA), and National Presidential Directive No. 40. The paper will then identify areas of potential weakness and gaps that exist in space launch programs as a whole and explore the security implications that impact the NSSL specifically. Finally, the paper will examine how the trajectory of the NSSL program could be adjusted in order to facilitate a smooth transition into new launch vehicles, while maintaining mission success, minimizing national security vulnerabilities, and clarifying the defense acquisition process.No embargoAcademic Major: EnglishAcademic Major: International Studie

The natural history of bugs: using formal methods to analyse software related failures in space missions

Space missions force engineers to make complex trade-offs between many different constraints including cost, mass, power, functionality and reliability. These constraints create a continual need to innovate. Many advances rely upon software, for instance to control and monitor the next generation ‘electron cyclotron resonance’ ion-drives for deep space missions.Programmers face numerous challenges. It is extremely difficult to conduct valid ground-based tests for the code used in space missions. Abstract models and simulations of satellites can be misleading. These issues are compounded by the use of ‘band-aid’ software to fix design mistakes and compromises in other aspects of space systems engineering. Programmers must often re-code missions in flight. This introduces considerable risks. It should, therefore, not be a surprise that so many space missions fail to achieve their objectives. The costs of failure are considerable. Small launch vehicles, such as the U.S. Pegasus system, cost around $18 million. Payloads range from$4 million up to $1 billion for security related satellites. These costs do not include consequent business losses. In 2005, Intelsat wrote off$73 million from the failure of a single uninsured satellite. It is clearly important that we learn as much as possible from those failures that do occur. The following pages examine the roles that formal methods might play in the analysis of software failures in space missions

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure

CUSTARD (Cranfield University Space Technology Advanced Research Demonstrator) - A Micro-System Technology Demonstrator Nanosatellite. Summary of the Group Design Project MSc in Astronautics and Space Engineering. 1999-2000, Cranfield University

CUSTARD (Cranfield University Space Technology And Research Demonstrator) was the group design project for students of the MSc in Astronautics and Space Engineering for the Academic Year 1999/2000 at Cranfield University. The project involved the initial design of a nanosatellite to be used as a technology demonstrator for microsystem technology (MST) in space. The students worked together as one group (organised into several subgroups, e.g. system, mechanical), with each student responsible for a set of work packages. The nanosatellite designed had a mass of 4 kg, lifetime of 3 months in low Earth orbit, coarse 3-axis attitude control (no orbit control), and was capable of carrying up to 1 kg of payload. The electrical power available was 18 W (peak). Assuming a single X-band ground station at RAL (UK), a data rate of up to 1 M bit s-1 for about 3000 s per day is possible. The payloads proposed are a microgravity laboratory and a formation flying experiment. The report summarises the results of the project and includes executive summaries from all team members. Further information and summaries of the full reports are available from the College of Aeronautics, Cranfield University

Space-based Aperture Array For Ultra-Long Wavelength Radio Astronomy

The past decade has seen the rise of various radio astronomy arrays, particularly for low-frequency observations below 100MHz. These developments have been primarily driven by interesting and fundamental scientific questions, such as studying the dark ages and epoch of re-ionization, by detecting the highly red-shifted 21cm line emission. However, Earth-based radio astronomy below frequencies of 30MHz is severely restricted due to man-made interference, ionospheric distortion and almost complete non-transparency of the ionosphere below 10MHz. Therefore, this narrow spectral band remains possibly the last unexplored frequency range in radio astronomy. A straightforward solution to study the universe at these frequencies is to deploy a space-based antenna array far away from Earths' ionosphere. Various studies in the past were principally limited by technology and computing resources, however current processing and communication trends indicate otherwise. We briefly present the achievable science cases, and discuss the system design for selected scenarios, such as extra-galactic surveys. An extensive discussion is presented on various sub-systems of the potential satellite array, such as radio astronomical antenna design, the on-board signal processing, communication architectures and joint space-time estimation of the satellite network. In light of a scalable array and to avert single point of failure, we propose both centralized and distributed solutions for the ULW space-based array. We highlight the benefits of various deployment locations and summarize the technological challenges for future space-based radio arrays.Comment: Submitte

Deep Space Network information system architecture study

The purpose of this article is to describe an architecture for the Deep Space Network (DSN) information system in the years 2000-2010 and to provide guidelines for its evolution during the 1990s. The study scope is defined to be from the front-end areas at the antennas to the end users (spacecraft teams, principal investigators, archival storage systems, and non-NASA partners). The architectural vision provides guidance for major DSN implementation efforts during the next decade. A strong motivation for the study is an expected dramatic improvement in information-systems technologies, such as the following: computer processing, automation technology (including knowledge-based systems), networking and data transport, software and hardware engineering, and human-interface technology. The proposed Ground Information System has the following major features: unified architecture from the front-end area to the end user; open-systems standards to achieve interoperability; DSN production of level 0 data; delivery of level 0 data from the Deep Space Communications Complex, if desired; dedicated telemetry processors for each receiver; security against unauthorized access and errors; and highly automated monitor and control