The Space Technology 5 (ST-5) mission successfully placed three micro-satellites in a 300 x 4500 km dawn-dusk orbit on 22 March 2006. Each spacecraft carried a boom-mounted vector fluxgate magnetometer that returned highly sensitive and accurate measurements of the geomagnetic field. These data allow, for the first time, the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured in low-Earth orbit on time scales of approximately 10 sec to 10 min. The constellation measurements are used to directly determine field-aligned current sheet motion, thickness and current density. In doing so, we demonstrate two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit; 1) the "standard method," based upon s/c velocity, but corrected for FAC current sheet motion, and 2) the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation. Future studies will apply these methods to the entire ST-5 data set and expand to include geomagnetic field gradient analyses as well as field-aligned and ionospheric currents.

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Space Technology 5 multi‐point measurements of near‐Earth magnetic fields: Initial results

Satellite constellations and Distributed Spacecraft Mission (DSM) architectures offer unique benefits to Earth observation scientists and unique challenges to cost estimators. The Cost and Risk (CR) module of the Tradespace Analysis Tool for Constellations (TAT-C) being developed by NASA Goddard seeks to address some of these challenges by providing a new approach to cost modeling, which aggregates existing Cost Estimating Relationships (CER) from respected sources, cost estimating best practices, and data from existing and proposed satellite designs. Cost estimation through this tool is approached from two perspectives: parametric cost estimating relationships and analogous cost estimation techniques. The dual approach utilized within the TAT-C CR module is intended to address prevailing concerns regarding early design stage cost estimates, and offer increased transparency and fidelity by offering two preliminary perspectives on mission cost. This work outlines the existing cost model, details assumptions built into the model, and explains what measures have been taken to address the particular challenges of constellation cost estimating. The risk estimation portion of the TAT-C CR module is still in development and will be presented in future work. The cost estimate produced by the CR module is not intended to be an exact mission valuation, but rather a comparative tool to assist in the exploration of the constellation design tradespace. Previous work has noted that estimating the cost of satellite constellations is difficult given that no comprehensive model for constellation cost estimation has yet been developed, and as such, quantitative assessment of multiple spacecraft missions has many remaining areas of uncertainty. By incorporating well-established CERs with preliminary approaches to approaching these uncertainties, the CR module offers more complete approach to constellation costing than has previously been available to mission architects or Earth scientists seeking to leverage the capabilities of multiple spacecraft working in support of a common goal.

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A Survey of Cost Estimating Methodologies for Distributed Spacecraft Missions

An objective for advanced satellites and spacecraft is to continually reduce both their size and mass. This reduction can place severe constraints on the thermal control systems. In addition, mission requirements also may dictate the need to alter the spacecraft energy profile during the course of the mission. To facilitate these advances, significant research has been conducted to develop variable emittance coatings and devices to provide active spacecraft thermal control. Several of these technologies have matured to a level where space based testing is feasible and will be performed as part of the ST5 new millennium spacecraft mission. One of these technologies utilizes electrostatic hold-down of a high emissivity composite film to actively control spacecraft skin temperature. This electrostatic radiator (ESR) device functions as a thermal switch and changes the mode of heat transfer between the spacecraft skin and the radiator film from conduction to radiation. This device has demonstrated large changes in effective emissivity in laboratory cold thermal vacuum testing. In this paper, the theory of operation of the ESR and the construction of the device as configured for demonstration on the ST5 mission is presented. The role of the ST5 mission in the maturation process for VEC technologies is discussed. This paper also describes test results for the ESR through flight qualification testing for the ST5 mission. Finally, anticipated operational characteristics and mission reliability estimates are provided.

Electrostatic radiator for satellite temperature control

In this paper, we describe possible natural formations for satellites in low Earth orbit that exploit the Earth's oblateness. These formations are based upon an analytic model of natural formations for satellites in nearly circular orbits, which has already been published, and explores the range of formations available. We describe how we parameterize the formations and then derive from this parameterization the orbital elements needed for each satellite orbit and then show the long-term evolution of these orbits to show the slow evolution of the formation geometry over time. We demonstrate that the formations maintain their projected shape in the sky without control over a day, in the presence of gravitational perturbations. This shows that the control requirements for long-term maintenance of such formations can be reduced considerably for long-term maintenance.

Designing Natural Formations of Low-Earth-Orbiting Satellites

Distributed satellite systems are large research topics, spanning many fields such as communications, networking schemes, high performance computing, and distributed operations.12 DARPA's F6 fractionated spacecraft mission is a prime example, culminating in the launch of technology demonstration satellites for autonomous and rapidly configurable satellite architectures. Recent developments at Surrey Space Centre have included the development of a Java enabled system-on-a-chip solution towards running homogenous agents and middleware software configurations.

Real-time agent middleware experiments on java-based processors towards distributed satellite systems

The Space Technology 5 project, currently in the implementation phase, is part of the National Aeronautics and Space Administration's New Millennium Program. Space Technology 5 is a constellation of three micro-satellites, with a target launch date of December 2005. A three-month flight demonstration phase is planned. Space Technology 5 addresses technology challenges for future micro-satellite missions, as well as test and operations strategies for multi-spacecraft missions. By validating the technologies, science capability and constellation concepts in flight, Space Technology 5 enables future missions to use these technologies and concepts at reduced risk. This paper describes the Space Technology 5 mission, and the applicability of the technologies, spacecraft, and mission concepts to future missions. It also discusses the validation approach for the Space Technology 5 mission in general.

Space Technology 5: pathfinder for future micro-sat constellations

The Space Technology 5 (ST5) Project, part of NASA's New Millennium Program, consists of a constellation of three micro-satellites The validation objectives are to demonstrate the research-quality science capability of the ST5 spacecraft; to operate the three spacecraft as a constellation; and to design, develop, test and flight-validate three capable micro-satellites with new technologies The project team has made significant progress in the past year in building and testing the ground system and flight hardware Through component-level testing and spacecraft integration and test, many components have been demonstrated on the ground to begin achieving the validation objectives We are on target for our February 28, 2006 launch date A three-month flight demonstration phase is planned, during which we complete the flight validation objectives This paper describes the validation strategy for science capability, constellation operations, and spacecraft and component technologies, as well as progress made to date

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Space Technology 5 - technology validation update

The Space Technology 5 (ST-5) project is part of NASA's new millennium program. The validation objectives are to demonstrate the research-quality science capability of the ST-5 spacecraft; to operate the three spacecraft as a constellation; and to design, develop, test and flight-validate three capable micro-satellites with new technologies. A three-month flight demonstration phase is planned, beginning in March 2006. This year, the mission was re-planned for a Pegasus XL dedicated launch into an elliptical polar orbit (instead of the originally-planned geosynchronous transfer orbit.) The re-plan allows the mission to achieve the same high-level technology validation objectives with a different launch vehicle. The new mission design involves a revised science validation strategy, a new orbit and different communication strategy, while minimizing changes to the ST-5 spacecraft itself. The constellation operations concepts have also been refined. While the system engineers, orbit analysts, and operations teams were re-planning the mission, the implementation team continued to make progress on the flight hardware. Most components have been delivered, and the first spacecraft is well into integration and test.

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C.C. Carlisle

Papers

Space Technology 5: pathfinder for future micro-sat constellations

Space Technology 5 - technology validation update

Space Technology 5 - changing the mission design without changing the hardware