Commercial Data Relay Services in the Cis-Lunar Environment With SSTL’s Lunar Pathfinder

Many missions are planned for the lunar environment in the coming decades. Traditionally, all missions would receive telecommands direct-from-Earth and send payload data and telemetry direct-to-Earth. However, missions can benefit from reduced size, weight, power and costs and increased data rates if they forgo space-borne direct-to/from-Earth communications hardware and instead communicate with a nearby cis-lunar data relay orbiter. Accordingly, SSTL has been working with the European Space Agency under the auspices of the Commercial Lunar Missions Support Services partnership agreement to provide Lunar communications and navigations services. This agreement will see SSTL design, build, test and operate the Lunar Pathfinder spacecraft, a small satellite with a mass of 300 kg that will be placed in an elliptical lunar frozen orbit. Lunar Pathfinder will launch in 2025, and from 2026, provide communications services to lunar missions of all types

Low Cost Hyperspectral Imaging From a Microsatellite

A 100 kg class SSTL microsatellite platform accommodating the Sira Compact High Resolution Imaging Spectrometer (CHRIS) can perform high spectral resolution imaging over multiple wavelengths. Hyperspectral imaging data may be used within a wide variety of applications ranging from precision agriculture and land use, to ocean colour monitoring, coastal and atmospheric studies. CHRIS operates in the 415 to 1050 nm wavelength band, with spectral sampling interval from 2 to 12 nm (depending on wavelength) and is programmable from the ground. Operating at 25 m ground sample distance the instrument can provide information over 19 spectral bands whilst at 50 m ground sample distance, for example, 63 bands can be imaged simultaneously. Flying CHRIS as the main payload on a SSTL microsatellite enables dedicated platform resources to exploit the huge potential of such a payload at low cost. The three-axis stabilised platform can off-point from nadir by ±30° to support accurate target selection. 48 Mbps payload data downlink rates, a 12 Gbyte data storage, and high efficiency GaAs panels for power provision all ensure a good payload duty cycle per orbit. The estimated spacecraft cost is 8.5 million GBP, resulting in affordable constellation options. A constellation of hyperspectral satellites providing high temporal resolution in addition to high spectral resolution could also be used to enhance the infrastructure of the Disaster Monitoring Constellation (DMC). The DMC is currently under construction at SSTL and is due for launch in 2002. This may be implemented either singly, or in constellations, via a ‘plug and play’ constellation approach. This paper describes how low cost hyperspectral imaging may be effectively accomplished using a microsatellite platform and looks at the potential benefits of implementing a series of these microsatellites in a constellation

Earthquake Forecast Science Research with a Small Satellite

Reliable, repeatable Earthquake forecast is a subject surrounded by controversy and scepticism. What is clear, is that reliable forecast could be the single most effective tool for earthquake disaster management. Roughly a third of the world’s population live in areas that are at risk and, every year since the beginning of the twentieth century earthquakes have caused an average of 20,000 deaths. The economic loss in the 1995 Kobe, Japan earthquake was greater than US$100 billion . Substantial progress has been made on the development of methods for earthquake hazard analysis on a timescale of a few decades. However, the forecast of specific earthquakes on timescales of a few years to a few days is a difficult problem. It has been proposed that satellites and ground-based facilities may detect earthquake precursors in the ionosphere a few hours or days before the main shock. This hypothesis is now backed by a physical model, derived by the Russian Academy of Sciences from statist ical studies, and an understanding of the main morphological features of seismoionospheric precursors - which allows them to be separated from background ionospheric variability. The main problems now are lack of regular global data and limited funding for what is considered to be financially risky research. Low -cost, small satellites offer a solution to these problems. A 100 kg class SSTL enhanced microsatellite, carrying a RAS topside sounder and complimentary payload, will be used to make regular measurements over seismically active zones around the globe. The low cost of the spacecraft offers a financially low -risk approach to the next step in this invaluable research. The spacecraft will make ionospheric measurements for systematic research into the proposed precursors. The aims will be to confirm or refute the hypothesis; define their reliability and reproducibility; and enable further scientific understanding of their mechanisms. In addition, forecasting of the magnitude of the events, as well as an indication of the seismic centre may also be possible. These mission data should also lead to improved knowledge of the physics of earthquakes, improved accuracy for GPS-based navigation models, and could be used to study the reaction of the global ionosphere during magnetic storms and other solar-terrestrial events. The paper presents an overview of the scientific basis, goals, and proposed platform for this research mission

VISTA – A Constellation for Real Time Regional Imaging

The role of satellites in medium and high-resolution reconnaissance of the Earth has been well demonstrated in recent years through missions such as Landsat, SPOT, IKONOS, ImageSat and Quickbird. The market for such data products is well served and likely to become more competitive with further very-high-resolution missions. Whereas commercial markets have concentrated on enhancing resolution, the small satellite sector has concentrated on reducing the cost of data products, and the development of systems providing niche services. One such area that can be well served by smaller satellites is the need for higher temporal resolution, as this typically requires a large number of satellites to operate as a constellation. Surrey is currently engaged in building its first constellation providing daily global coverage at moderate resolution in three spectral bands. Targeted at providing timely quick-look data products for disaster mitigation and monitoring, the constellation comprises 5 satellites in a single orbital plane. Each satellite has a wide swath so that successive satellites progressively cover the entire globe in a single day. The Vista constellation takes this concept a step further, and is proposed for applications requiring near-continuous surveillance of regional activity. By introducing a multiple plane constellation of small Earth Observation satellites, it is possible to monitor the entire globe continuously. The paper describes the system trades and outlines the scope of the performance that could be obtained from such a system. A cost model illustrates that the balance between launch and space segment costs must be reached by considering suitable replacement strategies, and that the system is highly sensitive to requirement creep. Finally, it is shown that the use of cost effective, small satellites leads to solutions previously thought to be out of reach of government customers

Frisbee – A Platform for a Small Satellite Science Swarms

The FRISBEE multi-mission platform is presented, alongside the mission concept for SWARM (Space Weather Advanced Research Mission), a fleet of 30 or more microsatellites launched in groups of 5 and covering a range of local times and inclinations. The aim of this mission is to develop an understanding of the dynamic, global, and multiscale solar terrestrial interactions. The scientific payload is restricted to a dc magnetometer and electrostatic charged particle (ion and electron) analyser, providing both high time resolution and characterisation of collisionless plasma processes. The baseline satellite swarm can be launched in a variety of configurations and be augmented by future launches of identical satellites to provide greater coverage and density of measurement. The satellites require only loose formation control to ensure equal separation throughout the set of orbits defined in this document. The individual satellites are spin stabilized and each have a mass \u3c 25 kg. This mission represents the next step in understanding the solar terrestrial interaction and the potential results will be of great interest to the space science community at large. This mission has a true requirement for a swarm such that it can sample the magnetosphere in three dimensions and with sufficient density of measurements. The spacecraft required for this proposed mission could be designed and built within 24 months as most of the platform and payload technologies are re-used from previous missions. The mission has the potential for international collaboration, with provision of spacecraft platforms and world-leading scientific research. A demonstration of this mission has been down-selected by the Particle Physics and Astronomy Research Council (PPARC) for potential funding in the UK National MOSAIC small satellite programme

Low Cost Planetary Exploration: Surrey Lunar Minisatellite and Interplanetary Platform Missions

In order to meet the growing global requirement for affordable missions beyond Low Earth Orbit, two types of platform are under design at the Surrey Space Centre. The first platform is a derivative of Surrey’s UoSAT-12 minisatellite, launched in April 1999 and operating successfully in-orbit. The minisatellite has been modified to accommodate a propulsion system capable of delivering up to 1700 m/s delta-V, enabling it to support a wide range of very low cost missions to LaGrange points, Near-Earth Objects, and the Moon. A mission to the Moon - dubbed “MoonShine” - is proposed as the first demonstration of the modified minisatellite beyond LEO. The second platform - Surrey’s Interplanetary Platform - has been designed to support missions with delta-V requirements up to 3200 m/s, making it ideal for low cost missions to Mars and Venus, as well as Near Earth Objects (NEOs) and other interplanetary trajectories. Analysis has proved mission feasibility, identifying key challenges in both missions for developing cost-effective techniques for: spacecraft propulsion; navigation; autonomous operations; and a reliable safe mode strategy. To reduce mission risk, inherently failure resistant lunar and interplanetary trajectories are under study. In order to significantly reduce cost and increase reliability, both platforms can communicate with low-cost ground stations and exploit Surrey’s experience in autonomous operations. The lunar minisatellite can provide up to 70 kg payload margin in lunar orbit for a total mission cost US$16-25 M. The interplanetary platform can deliver 20 kg of scientific payload to Mars or Venus orbit for a mission cost US$25-50 M. Together, the platforms will enable regular flight of payloads to the Moon and interplanetary space at unprecedented low cost. This paper outlines key systems engineering issues for the proposed Lunar Minisatellite and Interplanetary Platform Missions, and describes the accommodation and performance offered to planetary payloads

Breaking the Smallsat Barriers to Sub-50cm Imaging

New cutting-edge imaging sensors can now reduce instrument size and mass, leading to mission cost savings, and bring sub-50cm imaging capability into the realm of small satellites. Whilst aperture is essential to achieving resolution, half-pixel shifted sensor architectures decouple achievable Ground Sampling Distance (GSD) from the native ground projected pixel. This facilitates the deployment of Very High Resolution (VHR) small satellite constellations featuring improved Signal-to-Noise performance and increased area collection rates compared to push-frame systems. A fundamental limitation to the theoretical performance of an optical system is imposed by its aperture diameter; hence, for a given aperture, the aim is to maximize the information content resolved up to this limit. This is achieved by minimizing losses caused by aberrations in the optical system and enhancing platform stability on-orbit. Further information is lost due to aliasing at higher spatial frequencies; however, the recovery of such information is unlocked through the novel sensor technology and processing techniques proposed. Funded under the European Space Agency (ESA) “Investing in Industrial Innovation” (InCubed) program, this paper reports on the build and verification campaign of a sub-50cm capable instrument Proto-Flight Model (PFM), the beneficial properties of half-pixel offset sensors, and the platform supporting such a payload

BILSAT: Advancing Smallsat Capabilities

Small spacecraft technologies and capabilities are evolving to the point where the BILSAT 120kg spacecraft will this year demonstrate capabilities and performance similar to the 320kg UoSAT-12 mission launched in 1999. Over the past few years, the design of small satellites has evolved from simple curiosities to effective, high performance systems, capable of competing with much bigger and much more expensive spacecraft. Within the framework of an agreement between SSTL and TUBITAK-BILTEN (The Information Technologies and Electronics Research Institute), a non-profit government laboratory located in Ankara, Turkey, a Technology Transfer Program was started in August 2001. This program includes the design, manufacture and launch of one Enhanced SSTL microsatellite platform, one engineering model for use in Turkey and the training of engineers in all aspects of the spacecraft design. Detailed design began using the Enhanced SSTL microsatellite platform as the starting point. The end product that will be launched in the summer of 2003, is the most advanced spacecraft ever designed by SSTL, carrying two advanced payloads developed by TUBITAK-BILTEN. The spacecraft is a highly optimised satellite, with a mass of 120kg and including 14 cameras (in several imager arrangements), a 10m/s class resistojet propulsion system, VHF/UHF and S-band RF systems, tried and tested OBDH units in parallel with newly designed mass data storage and processing units, all this topped by a high performance AODCS subsystem, including two star trackers, GPS receiver (for both orbit and attitude determination), rate gyros, four momentum/reaction wheels, and what will be the first operational use of Control Momentum Gyros on a small spacecraft, to perform high agility manoeuvres. These units will be used to achieve the missions specified for this project, mainly full imaging of Turkey, stereoscopic imaging of selected targets, a Digital Elevation Map of Turkey, and communications. The present paper discusses briefly the technical characteristics of the spacecraft, but focuses on the mission aspects and how the different subsystems (namely the new subsystems and payloads) will be used to accomplish the mission. The operational modes of the spacecraft are discussed and the interaction of the AODCS subsystem with the OBDH and Imaging system is described in detail

Tweeting From the Moon

Lunar Communications Pathfinder is planned to enable small and large satellites and landers to carry out data intensive missions around the moon, without the need for complex and costly on-board communication equipment and access to global ground networks. From the middle of this decade there are expected to be 5 to 15 active space missions on or around the moon, generating several GBytes of data per day. Lunar Communications Pathfinder is a commercial initiative with ESA and NASA as anchor tenants. The 300kg class small spacecraft is currently in manufacture for launch in 2025, and is aimed at alleviating pressure on the Deep Space Network. It will provide a commercial high speed communications service that will enable landers, orbiters, and even CubeSats to operate around the moon without requiring direct line of sight with the Earth. A small user terminal is in development as part of the service package, and a mission builder tool has been made available for planning purposes for prospective users. LCP provides a high speed intersatellite link back to Earth for a planned 8 year mission. The system is planned to be extended further with additional spacecraft, opening up the potential to provide a more comprehensive communications and navigation service. Building on LCP, the ESA Moonlight initiative has contracted a study phase in order to develop the plans for the full constellation service beyond this initial spacecraft. LCP demonstrates how small satellites can provide innovative commercial services, and enable the ability for other small satellites and landers to carry out data intensive missions. This paper will detail the spacecraft, the system design trades, and how the service is expected to evolve

Merlion L & S Band System

Under the MERLION project name, Nanyang Technological University of Singapore has teamed up with Surrey Satellite Technology Ltd. of the UK and developed a sophisticated communication payload on the UoSAT-12 mini-satellite which was launched recently. The MERLION payload combines an analogue and digital regenerative transponder, with L-band uplink and S-band downlink. The transponder can be configured in-orbit for a variety of functions and experiments, and carries dual signal processors. The digital uplink comprises a frequency agile L-band receiver, and 9600bps FSK and IMbps BPSK demodulators. The frequency agile digital S-band downlink is intended for high speed data transfer and will be employed to perform a variety of communication experiments. It is also capable of low bit rate spread spectrum communications, together with convolutional coding options to investigate its performance in the highly dynamic environment of LEO. The downlink can be configured to perform link characterisation at these frequencies. In conjunction with the 80386EX based On-Board-Computers, the digital uplink and downlink system can be configured into a high rate Store-and-Forward transponder. This paper would introduce the basic Medion architecture and design considerations, to realise the above functionality within the scope of a low cost mission