NASA Research Announcement: Formation Navigation, Control, and Mission Design Algorithms

General Information

• Document Type: Presolicitation Notice
• Solicitation Number: NRA-03-GSFC-AETD-01
• Posted Date: Feb 04, 2003
• Original Response Date: Mar 14, 2003
• Original Archive Date: Feb 04, 2004
• Current Archive Date:
• Classification Code: A — Research & Development

Contracting Office Address

NASA/Goddard Space Flight Center, Code 210.M, Greenbelt, MD 20771

Description

This NASA Research Announcement (NRA) solicits proposals for investigations of navigation, control, and mission design algorithms that enable and/or enhance formation flying and distributed sensing missions. The program goals are not mission specific.

This NRA solicits proposals that will develop revolutionary flight dynamics and control technologies supporting fault-tolerant Guidance, Navigation, and Control (GN&C) systems for distributed space systems (DSS) in any orbit. In particular, it seeks investigations that will utilize new principles, such as dynamical systems theory, decentralized and nonlinear control, and analytic redundancy. Of equal interest are new technology concepts, including safe mode for formations, and, the use of drag and solar radiation pressure for orbit control. Also of equal interest are proposals that perform proofs of concept, algorithm validations, and flight software prototyping. Of further and equal interest are proposals studying spacecraft formation guidance and trajectory planning. Proposers should seek to demonstrate algorithms that will allow for the minimization of initial launch mass and the maximization of mission duration, using current state of the art and next generation technologies. The focus of this NRA is primarily on mission design, guidance, navigation, and control of the absolute and relative orbits of formation flying spacecraft, and as such it does not explicitly solicit research on attitude determination and control. However, a focus on the six degree of freedom (6DOF) problem as is pertinent to formation flying analysis will have potential for a higher degree of preference than solely investigating the orbital relative navigation and/or control problem. It will be essential that the fundamental issues of orbital mechanics are adequately addressed in either case. Specifically, the technology areas solicited by this NRA include: 1. Precision Formation Control Architectures. This topic includes all aspects of absolute and relative trajectory tracking of nominal trajectories, based on the benchmark problems described below. Relative stationkeeping is of greater interest than control of the overall formation?s state, but approaches that address both problems together are encouraged. Both propulsive and non-propulsive (e.g. solar sail-type) maneuvering techniques may be considered.

Investigators are encouraged to study nominal stability and performance as well as robustness to model uncertainties and disturbances. In general, simpler approaches are preferred, and investigators should plan to address implementability in terms of current or next generation sensors, actuators, and onboard computers. Of primary interest to this NRA are the following subtopics: 1a. Control of Earth Orbiting Missions. This subtopic covers all missions in which the gravitational influence of the earth is the primary external force. Applicability to other bodies is of minor interest. Disturbances that should be considered include but are not limited to drag, solar radiation pressure, and non-primary gravitational bodies. Of particular interest in this call are the LEO and HEO benchmark problems described below. 1b. Control of Libration Point Missions. This subtopic covers all missions in which the gravitational influence of at least two major bodies plays a significant role, so that approximations of the three-body problem of Lagrange are applicable. Of major interest are missions in large repeating trajectories around the co-linear equilibrium points surrounding the secondary body, and in particular, the Sun-Earth/Moon system is of interest, as the benchmark problem below describes. Control of ?deep-space? missions, in which the sun may be considered as the central body, is of secondary interest in this NRA, but approaches that are equally applicable to both ?deep space? missions and either or both of the above subtopics are of special interest. 2. Precise Relative Navigation for High Earth and Libration Point Missions. This topic includes all aspects of relative orbit determination based on the benchmark problems described below, but especially on the HEO and libration point missions. Relative navigation is of greater interest than estimation of the overall formation?s state, but approaches that address both problems together are encouraged.

Navigation algorithms of interest include, but are not limited to, those that perform relative and simultaneous navigation of multiple spacecraft using GPS beyond LEO, celestial navigation, very-high-precision relative ranging techniques using optical and radio frequency cross-links, and passive techniques such as reflected GPS and angles-only relative state measurements. Realistic sensor biases and random disturbances should be considered. 3. Design of Formations. This topic includes all aspects of mission design and formation guidance law development, including specification of nominal absolute and relative trajectories for initialization, reconfiguration, and decommissioning. This topic is not constrained to the benchmark problems described below. Due to significant differences in dynamics, this topic is divided into the following subtopics: 3a. Design of Earth Orbiting Missions. This subtopic covers all missions in which the gravitational influence of the earth is the primary external force. Applicability to other bodies is of minor interest. 3b. Design of Libration Point Missions. This subtopic covers all missions in which the gravitational influence of at least two major bodies plays a significant role, so that approximations of the three-body problem of Lagrange are applicable. Of major interest are missions in medium to large amplitude repeating trajectories around the co-linear equilibrium points surrounding the secondary body, and in particular, the Sun- Earth/Moon system is of interest. Design of ?deep-space? missions, in which the sun may be considered as the central body, is of secondary interest in this NRA, but approaches that are equally applicable to both ?deep space? missions and either or both of the above subtopics are of special interest. 4. Fault Tolerance, Collision Avoidance, and Formation Safe Hold. This is an interdisciplinary topic that includes all aspects of relative trajectory estimation and control in off-nominal circumstances, such detected and undetected failures and significant degradations of performance in sensors, actuators, communications systems, onboard processors or busses, etc. It also covers all aspects of predicting unplanned close approaches and any other anomalies that would require that the formation enter a stable ?safe mode? of operations.

Design of such ?safe mode? formation configurations that would allow time for recovery operations without loss of the formation due to collision, dispersal, or other circumstances is of special interest. Algorithms for fault detection, identification, and recovery are of interest, as are control and estimation architectures that enhance overall mission reliability via distribution or decentralization of the estimation, guidance, and/or control computations. In addition to technology that leads to lower mission costs by directly lowering mission element costs, technology development that lowers development cost by lowering risk will also be evaluated favorably. Finally, demonstration of a possible commercial application and/or application to future NASA, DoD, or commercial missions will also be considered positively. To provide high-level focus to the research, NASA is supplying the following benchmark problems. These problems are not specific to any current or proposed mission, but instead are intended to capture high-level features that would be generic to many similar missions. Proposers are requested but not required to use these problems as the basis of test cases for their technology concepts. Low Earth Orbit. The formation is defined by a reference point, which follows a sun-synchronous orbit with a nominal altitude of 400 km. There are six 3-axis stabilized spacecraft, three equally spaced in each of two oppositely inclined ?projected circular? formations 500 m in diameter. That is, when projected into the local horizontal plane, the paths of relative motion about the reference (there are two such paths containing the two sets of three spacecraft) are circles. This relative motion can be achieved through a combination of differences in the orbital elements from the reference. The planes of relative motion are then inclined +/-26.6 degrees relative to the local horizontal plane. The relative positions of the spacecraft should be controlled with respect to their desired relative trajectories to within 5 m or better. The nominal mission duration is two years. High Earth Orbit. The average position of the formation follows a 1.2 by18 Earth radii orbit, lying in the ecliptic plane, where the initial line of apsides is parallel to the direction to the sun, and apogee is opposite the sun. There are four spin-stabilized spacecraft that must form a 10 km regular tetrahedron at apogee, with arbitrary orientation.

A tetrahedral configuration need not be maintained at any other point in the orbit. The spacecrafts? spin rate is 20 RPM, and the spin axis is perpendicular to the ecliptic plane. The spacecrafts? relative positions should be controlled to within 10% of the separation at apogee, subject to a 1 km minimum separation constraint throughout the orbit. The nominal mission duration is two years. Libration Point. The formation follows a medium lissajous orbit about the trans-terrestrial, now commonly known as ?L2,? co-linear libration point of the Sun-Earth/Moon system, with y amplitude of approximately 300,000 km and z amplitude equal to or less than the y amplitude. There are 20 3 axis stabilized spacecraft, each a subaperture along an aspherical surface with a 250 m radius. The subapertures are distributed over the asphere in an arbitrary configuration so as to produce a large number of internal baselines internal to a sparse primary telescope aperture. A single spacecraft is located 100 km away at the focus, along the line of sight to the science target, such that the whole configuration forms a distributed Fizeau interferometer.

There two modes of operation: A science mode, in which the aperture must ?stare? in an inertially fixed direction for up to a month, with relative positions controlled to within 1 cm. While staring, the formation must rotate about the line of sight to the target at least once per week, and the internal baselines of the aperture must vary somewhat arbitrarily during the rotation. A maneuver mode, in which the line of sight of the aperture must slew on the order of 20 degrees per day to acquire a new science target. The nominal mission duration is 12 years. Participation in this program is closed to NASA Centers and the Jet Propulsion Laboratory, but otherwise open to all categories of domestic organizations, including educational institutions, profit and nonprofit organizations, and other Government agencies. Historically Black Colleges and Universities, other minority educational institutions, and small businesses and organizations owned and controlled by socially and economically disadvantaged individuals or women are particularly encouraged to apply. The entirety of this NRA may be found and downloaded in a variety of standard formats on the web site: http://gsfctechnology.gsfc.nasa.gov/nraannouncements.htm

Proposals in response to this NRA may request periods of performance for up to three years. NASA’s ability to fund the proposals selected under this NRA is contingent upon the availability of appropriated funds. Approximately $1 million per year is expected to be available to support this program, and it is expected that awards in the range of $50,000-$100,000 per year will be made. There will be two types of awards: (a) <$60,000: most of the awards will be of this nature and these will be funded at one time. (b) $100,000 - $120,000: a few will awarded at this value and the funds will be sent incrementally throughout the year. A single institution and/or investigator may apply for more than one award, and to more than one technology area. Many of the awards will take the form of grants and cooperative agreements; note that http://genesis.gsfc.nasa.gov/grants/grants.htm contains information about the requirements and regulations covering these types of awards, as well as information about current and pending awards.

Winning proposers are expected to work closely with Goddard Space Flight Center?s Distributed Space Systems team, http://gsfctechnology.gsfc.nasa.gov to integrate their technologies with GSFC?s efforts, and to demonstrate the technical maturity of their investigations via high-fidelity relevant test environments, such as the GSFC?s Formation Flying Testbed. Such demonstrations might represent an actual system application or might only be similar to the planned application using the same technologies. NASA reserves the right to make any data developed under this NRA public. It is expected that winning proposers will submit a final report that contains detailed design information, including full mathematical description, source code, and schematics as appropriate. These reports will be published in a series of NASA contractor reports, which are subject to export controls (see http://www.hq.nasa.gov/office/codei/nasaecp for details). The final results of the investigation must also be summarized in the open literature in recognized professional journals and/or conference proceedings.

Note that the organization sponsoring this award requires that all publications sponsored by it be submitted to an internal NASA review prior to presentation or publication in any public forum. Notice of Intent (NOI) to propose: Due date: February 21, 2003 Address for submission: E-mail: Jesse.A.Leitner@nasa.gov or Fax: 301-286-1719 Submission of Proposal:

Required number:Five(5)hard copies-Four(4)copies plus signed original or electronic submission: http://gsfctechnology.gsfc.nasa.gov/nraannouncements.htm User name and password to perform the electronic submission can be obtained by sending an e-mail to maria.m.so@nasa.gov. (NOTE: It may take about a week to obtain the user account.) Due date March 14, 2003 by 4:30 p.m (EST)

Address for delivery by U.S. Postal Service, personal courier, or commercial service: Dr. Jesse Leitner Code 570 Goddard Space Flight Center Greenbelt, MD 20771 Attn: Distributed Spacecraft Technology Program Program Executive for further information: Dr. Jesse Leitner Code 570 Goddard Space Flight Center Greenbelt, MD 20771 or Ms. Maria So Code 570 Goddard Space Flight Center Greenbelt, MD 20771

Original Point of Contact

Eric Jackson Newman, Contract Specialist, Phone (301) 286-4240, Fax (301) 286-1720, Email enewman@pop200.gsfc.nasa.gov – Elizabeth Austin, Contracting Officer, Phone (301) 286-6843, Fax (301) 286-1720, Email Elizabeth.J.Austin@nasa.gov

Email your questions to Eric Jackson Newman at enewman@pop200.gsfc.nasa.gov