TOPMEX-9 distributed SAR mission employing nanosatellite cluster

2002

This paper describes a proposal for a rapid, low cost, nanosatellite mission to demonstrate the concept of GPS ocean reflectometry and to investigate the feasibility of determining sea state for a future operational space-based storm warning systems. The aims of this mission are to prove the general feasibility of GPS ocean reflectometry, to demonstrate sea state determination and to enable the development of a practical GPS ocean reflectometry payload for future missions. The payloads on the satellite consist of a 24 channel C/A code SGR-10 space GPS receiver and a solid state data recorder. The GPS receiver has one standard RHCP zenith antenna, and one high gain LHCP nadir antenna for receiving the reflected signals. A dual approach is taken to measurement gathering. Initially, bursts of directly sampled IF data are stored and downloaded to permit processing of the data on the ground. Later in the mission, the GPS receiver software may be modified to permit the processing of signals on-board the satellite. The nanosatellite is based on SSTL's SNAP design and has a projected total mass of around 12 kilograms; orbit average power of approximately 4.8 watts; 3-axis attitude control to 1-2 degrees; VHF uplink, S-band downlink at 500 kbps, and OBC based on the StrongARM SA1100. Using the SNAP design enables a fast manufacture at low cost: estimated at 9 months and around 2 million Euros, including launch. The proposed mission makes use of the Surrey Space Centre Mission Control ground-station in Guildford (UK) for control and data gathering. Surrey Satellite Technology Ltd (SSTL) is a world leader in both nanosatellite and GPS technology for small satellites. SSTL's highly successful SNAP-1 nanosatellite launched in June 2000 demonstrated the potential of such small spacecraft, and this proposal involves the first ever use of a nanosatellite for a commercial application (GANDER) in collaboration with SOS Ltd (UK) a company specialising in oceanography from space.

The Microwave Radiometer Technology Acceleration (MiRaTA) is a 3U CubeSat NASA Earth Science Technology Office (ESTO) mission under development for a 2016 launch. Microwave radiometry and GPS radio occultation (GPSRO) measurements of all-weather temperature and humidity provide key contributions toward improved weather forecasting. The MiRaTA mission will validate new technologies in both passive microwave radiometry and GPS radio occultation: (1) new ultra-compact and low-power technology for multi-channel and multi-band passive microwave radiometers, and (2) new GPS receiver and patch antenna array technology for GPS radio occultation retrieval of both temperature-pressure profiles in the atmosphere and electron density profiles in the ionosphere. In addition, MiRaTA will test (3) a new approach to spaceborne microwave radiometer calibration using adjacent GPSRO measurements. Radiometer measurement quality can be substantially improved relative to present systems through the use of proximal GPSRO measurements as a calibration standard for radiometric observations, reducing and perhaps eliminating the need for costly and complex internal calibration targets. MiRaTA will execute occasional pitch-up maneuvers so that radiometer and GPSRO observations sound overlapping volumes of atmosphere through the Earth's limb. To validate system performance, observations from both microwave radiometer (MWR) and GPSRO instruments will be compared to radiosondes, global high-resolution analysis fields, other satellite observations, and to each other using radiative transfer models. Both the radiometer and GPSRO payloads, currently at TRL5 but to be advanced to TRL7 at mission conclusion, can be accommodated in a single 3U CubeSat. The current plan is to launch from an ISS orbit at ~400 km altitude and 52° inclination for low-cost Blackwell and Cahoy, et al. 2 28 th Annual AIAA/USU Conference on Small Satellites validation over a ~90-day mission to fly in 2016. MiRaTA will demonstrate high fidelity, well-calibrated radiometric sensing from a nanosatellite platform, thereby enabling new architectural approaches for mission implementation at lower cost and risk with more flexible access to space.

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2003

The current emphasis in the satellite industry is on replacing large satellite platforms with one or more smaller satellites, built at lower cost, yet able to accomplish similar mission objectives. However, it is recognized that such small satellites pose severe constraints on payload volume, mass and power. Thus, the power constraint of synthetic-aperture-radar (SAR) imaging is such that a microsatellite would seem inappropriate. The primary reason for the high-transmit-power requirement is that traditional SAR systems collect the backscatter. Thus, if the forward-scattered element is collected, then the resultant reduction in transmit-power could make it feasible for installation on a microsatellite. Based upon this principle, a novel method by which two microsatellites`®y' in a speci c formation to accomplish an SAR imaging mission, bistatically, is proposed. The satellites view a swath of 30 km (chosen to limit the amount of data), at a ground resolution of 30 m, from an altitude of 700 km. The transmitting satellite will be thè master', with the receiver satellite`slaved' o¬ it for synchronization. Applications to a polar-ice-monitoring mission are discussed.

2009

The COM DEV Nanosatellite Tracking of Ships (NTS) spacecraft was launched at the end of April 2008 following an unprecedented 8-month kick-off to launch cycle. The mission has been operating successfully for almost one year, exceeding its life requirement of one-month and goal of 6-months. The NTS is producing valuable results from its Automated Identification System (AIS) payload which was designed to collect messages from maritime vessels around the globe. This paper presents the NTS mission results to date, the extensions to the mission as a consequence of its success and the impact of this responsive space activity on other upcoming missions. It is shown how much can be achieved operationally, in very little time, with a limited but focused mission capability.

This paper discusses the use of small satellites for future radar remote sensing applications. After a short introduction, we give first an overview of the TanDEM-X mission to be launched in autumn 2009. Here, special emphasis is put on the demonstration of innovative synthetic aperture radar (SAR) imaging techniques. Then, novel SAR configurations are introduced which make synergistic use of multiple small satellites flying in close formation. Performance examples demonstrate their unique capabilities for advanced Earth observation applications. Among these opportunities are the generation of digital elevation models with decimetre accuracy, the monitoring of ocean currents, and the measurement of small vertical displacements from snow accumulation, vegetation growth, and thawing permafrost soils. Challenges associated with the use of small satellites are pointed out and solutions to overcome them are presented.

A new way to perform space missions utilizes the concept of clusters of satellites that cooperate to perform the function of a larger, single satellite. Each smaller satellite communicates with the others and shares the processing, communications, and payload or mission functions. The required functionality is thus spread across the satellites in the cluster, the aggregate forming a "virtual satellite". The Air Force Research Laboratory (AFRL) initiated the TechSat 21 program to explore the basic technologies required to enable such distributed satellite systems. For this purpose, Space Based Radar (SBR) was selected as a reference mission to help identify technology requirements and to allow an easy comparison to a conventional approach. A summary of the basic mission and the performance requirements is provided. This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Goddard is providing advanced crosslink communication and navigation hardware and flight algorithms to demonstrate formation flying. Numerous industry partners are also supporting the universities with hardware, design expertise, and test facilities. Areas of particular interest to the TechSat 21 program include autonomous operation and simplified ground control of satellite clusters, intersatellite communications, distributed processing, and formation control. This paper summarizes both hardware and computational challenges that have been identified in both the TechSat 21 and the university nanosatellite programs for implementing operational satellite subsystems to accomplish these tasks.

Remote Sensing, 2022

The Canadian RADARSAT Constellation Mission (RCM) has passed its early operation phase with the performance evaluation being currently active. This evaluation aims to confirm that the innovative design of the mission’s synthetic aperture radar (SAR) meets the expectations of intended users. In this study, we provide an overview of initial results obtained for three high-priority applications; flood mapping, sea ice analysis, and wetland classification. In our study, the focus is on results obtained using not only linear polarization, but also the adopted Compact Polarimetric (CP) architecture in RCM. Our study shows a promising level of agreement between RCM and RADARSAT-2 performance in flood mapping using dual-polarized HH-HV SAR data over Red River, Manitoba, suggesting smooth continuity between the two satellite missions for operational flood mapping. Visual analysis of coincident RCM CP and RADARSAT-2 dual-polarized HH-HV SAR imagery over the Resolute Passage, Canadian Central ...

2009

Our nation has a truly impressive array of space-based capabilities supporting our armed forces. However, much of this support is focused at the strategic and operational levels of war. There are several areas of desired improvement in the space force enhancement mission area at the tactical level of war that could be addressed by small, inexpensive satellites dedicated for use by tactical land warfighters. One of these areas of desired improvement is tactical beyond-line-of-sight (BLOS) communications, including support for ground sensors, text message relay, voice communications, and image or video transmission. Technical solutions to fill these areas of desired improvement should be relatively inexpensive, and more importantly, taskable by tactical users in the area of operations. New trends in the miniaturization of electronic components are leading to smaller satellites with significant capabilities in the nanosatellite (1-10 kg) and microsat (10-100 kg) classes. For example, the CubeSat standard for nanosatellites now being built by universities around the world is based on tiny cube-shaped satellites with dimensions of only 10cm on a side and weighing about 1 kg. Slightly larger nanosatellite configurations, with multiple cube formats, allowing for missions from low earth orbit with broader scopes are under investigation by organizations such as NASA, Boeing, and the US Army. One technical approach that could address today's tactical BLOS communications area of desired improvement for the tactical warfighter would be a constellation of nanosatellites in low earth orbit. To investigate the feasibility of such a constellation, the US Army Space and Missile Defense Command/Army Forces Strategic Command (USASMDC/ARSTRAT) is executing the Space and Missile Defense Command-Operational Nanosatellite Effect, or SMDC-ONE, technology demonstration. The key SMDC-ONE demonstration thresholds for success involve designing, developing, building and qualification testing of two nanosatellite units, and acceptance testing of eight flight units within a one-year timeframe ending in April 2009. A custom communications payload will deliver a capability to support simulated ground sensors and text message relay. Communications beyond this level of complexity were not included in this demonstration to reduce schedule risk. SMDC-ONE can help establish the case for inexpensive space force enhancement for the tactical warfighter through relatively inexpensive, rapidly developed nanosatellite constellations.

Remote Sensing, 2020

The paper analyses an along-track multistatic Synthetic Aperture Radar (SAR) formation. The formation aims at achieving a high azimuth resolution maintaining at the same time a large swath width. The case with one transmitting sensor and all receiving is analyzed (Single Input Multiple Output, SIMO). An effective and novel reconstruction, in the two-dimensional frequency domain is introduced that is able to keep low the azimuth ambiguity and achieve a recombination gain close to the theoretical one. Degradation of the system performance due to the loss of the control of formation position is analyzed using probabilistic considerations. Moreover, some innovative methods to mitigate the loss of optimality are introduced and evaluated using simulations. Finally, considerations on the impact of the across-track non zero baseline are discussed.

1997

Two Earth-orbiting radar missions are planned by NASA-Shuttle Radar Topography Mission (SRTM) and LightSAR. The SRTM will fly aboard the Shuttle using interferometric synthetic aperture radar (IFSAR) to provide a global digital elevation map. SRTM is jointly sponsored by NASA and the National Imagery and Mapping Agency (NIMA). The LightSAR will utilize emerging technology to reduce mass and life-cycle costs for a mission to acquire SAR data for Earth science and civilian applications and to establish commercial utility. LightSAR is sponsored by NASA and industry partners. The use of IFSAR to measure elevation is one of the most powerful and practical applications of radar. A properly equipped spaceborne IFSAR system can produce a highly accurate global digital elevation map, including cloud-covered areas, in significantly less time and at significantly lower cost than other systems. For accurate topography over a large area, the interferometric measurements can be performed simultaneously in physically separate receive systems. The Spaceborne Imaging Radar C (SIR-C), successfully flown twice in 1994 aboard the Space Shuttle Endeavour, offers a unique opportunity for global multifrequency elevation mapping by the year 2000. The addition of a C-band receive antenna of approximately 60 m length, extended from the Shuttle bay on a mast, and operating in concert with the existing SIR-C antenna, produces an interferometric pair. It is estimated that the 90 percent linear absolute elevation error achievable is less that 16 meters for elevation postings of 30 meters. The SRTM will be the first single-pass spaceborne IFSAR instrument and will produce a near-global high-resolution digital topography data set