Spacecraft experiment pointing and attitude control system Patent

Development of spacecraft experiment pointing and attitude control syste

Low frequency VLBI in space using GAS-Can satellites: Report on the May 1987 JPL Workshop

Summarized are the results of a workshop held at JPL on May 28 and 29, 1987, to study the feasibility of using small, very inexpensive spacecraft for a low-frequency radio interferometer array. Many technical aspects of a mission to produce high angular resolution images of the entire sky at frequencies from 2 to 20 MHz were discussed. The workshop conclusion was that such a mission was scientifically valuable and technically practical. A useful array could be based on six or more satellites no larger than those launched from Get-Away-Special canisters. The cost of each satellite could be $1-2M, and the mass less than 90 kg. Many details require further study, but as this report shows, there is good reason to proceed. No fundamental problems have been discovered involving the use of untraditional, very inexpensive spacecraft for this type of mission

Adaptive mass expulsion attitude control system

An attitude control system and method operative with a thruster controls the attitude of a vehicle carrying the thruster, wherein the thruster has a valve enabling the formation of pulses of expelled gas from a source of compressed gas. Data of the attitude of the vehicle is gathered, wherein the vehicle is located within a force field tending to orient the vehicle in a first attitude different from a desired attitude. The attitude data is evaluated to determine a pattern of values of attitude of the vehicle in response to the gas pulses of the thruster and in response to the force field. The system and the method maintain the attitude within a predetermined band of values of attitude which includes the desired attitude. Computation circuitry establishes an optimal duration of each of the gas pulses based on the pattern of values of attitude, the optimal duration providing for a minimal number of opening and closure operations of the valve. The thruster is operated to provide gas pulses having the optimal duration

Cubesat Attitude Control Utilizing Low-Power Magnetic Torquers & A Magnetometer

Thesis (Ph.D.) University of Alaska Fairbanks, 2011The CubeSat Project has lowered development time and costs associated with university satellite missions that conform to their 10 centimeter cube design specification. Providing attitude control to a spacecraft, of such small volume, with a very limited power budget has been a challenge around the world. This work describes the development of an attitude control system based on a very low-power magnetic torquer used in conjunction with a magnetometer. This will be the first flight use of this torquer which is composed of a hard magnetic material wrapped inside of a solenoid. By discharging a capacitor through the solenoid, the magnetic dipole moment of this permanent magnet can be reversed. The completed attitude control system will make the first use of the low-power magnetic torquer to arrest satellite tip-off rates. It will then make the first known use of a dual axis magnetic dipole moment bias algorithm to achieve three-axis attitude alignment. The complete system is standalone for high inclination orbits, and will align the spacecraft to within 5 degrees of ram, nadir, and local vertical, without any requirement for attitude determination. The system arrests tip-off rates of up to 5� per second (in all 3 axes) for a satellite in a 600 kilometer polar orbit expending 0.56 milliwatts of power. Once in the proper alignment, it utilizes 0.028 milliwatts to maintain it. The system will function for low inclination orbits with the addition of a gravity boom. The system utilizes the magnetometer to calculate spacecraft body rates. This is the only known use of a magnetometer to directly measure spacecraft body rates without prior knowledge of spacecraft attitude

A Study Of Coupled Magnetic Fields For An Optimum Torque Generation

Magnetic torquers are specifically designed to generate a magnetic field onboard the satellites for their attitude control. A control torque is generated when the magnetic fields generated by the magnetic torquers couple with the geomagnetic fields, whereby the vector of the generated torque is perpendicular to both the magnetic fields

Attitude Determination and Control Systems

The importance of accurately pointing spacecraft to our daily lives is pervasive, yet somehow escapes the notice of most people. In this section, we will summarize the processes and technologies used in designing and operating spacecraft pointing (i.e. attitude) systems

The COLD-SAT Experiment for Cryogenic Fluid Management Technology

Future national space transportation missions will depend on the use of cryogenic fluid management technology development needs for these missions. In-space testing will be conducted in order to show low gravity cryogenic fluid management concepts and to acquire a technical data base. Liquid H2 is the preferred test fluid due to its propellant use. The design of COLD-SAT (Cryogenic On-orbit Liquid Depot Storage, Acquisition, and Transfer Satellite), an Expendable Launch Vehicle (ELV) launched orbital spacecraft that will perform subcritical liquid H2 storage and transfer experiments under low gravity conditions is studied. An Atlas launch vehicle will place COLD-SAT into a circular orbit, and the 3-axis controlled spacecraft bus will provide electric power, experiment control, and data management, attitude control, and propulsive accelerations for the experiments. Low levels of acceleration will provide data on the effects that low gravity might have on the heat and mass transfer processes used. The experiment module will contain 3 liquid H2 tanks; fluid transfer, pressurization and venting equipment; and instrumentation

Integrated Magnetic Management of Stored Angular Momentum in Autonomous Attitude Control Systems

Autonomous spacecraft operations are at the front end of modern research interests, because they enable space missions that would not be viable only with ground control. The possibility to exploit onboard autonomy to deal with platform management and nominal housekeeping is thus beneficial to realize complex space missions, which could then rely on ground support only for the mission-critical phases. One routine operation that most spacecraft must perform is stored angular momentum management to maintain fully usable momentum exchange actuators. The execution of this activity may be scheduled, commanded from the ground, or automatically triggered when certain thresholds are reached. However, autonomous angular momentum management may interfere with other primary spacecraft operations if executed with a dedicated and separate system mode. This paper presents the magnetic management of stored angular momentum, integrated with the main attitude control system. The system design and implementation are intended for autonomous spacecraft, and it can be operated without significant ground support. The paper describes the system architecture and the attitude control laws integrated with the magnetic angular momentum management. Specifically, the capability of the autonomous system to keep the internal angular momentum far from the saturation and far from the zero-crossing levels is highlighted. The performance of an example attitude control system with four reaction wheels and three magnetic torquers is presented and discussed, with the simulation results at model-in-the-loop (MIL) level

AXTAR: Mission Design Concept

The Advanced X-ray Timing Array (AXTAR) is a mission concept for X-ray timing of compact objects that combines very large collecting area, broadband spectral coverage, high time resolution, highly flexible scheduling, and an ability to respond promptly to time-critical targets of opportunity. It is optimized for submillisecond timing of bright Galactic X-ray sources in order to study phenomena at the natural time scales of neutron star surfaces and black hole event horizons, thus probing the physics of ultradense matter, strongly curved spacetimes, and intense magnetic fields. AXTAR's main instrument, the Large Area Timing Array (LATA) is a collimated instrument with 2-50 keV coverage and over 3 square meters effective area. The LATA is made up of an array of supermodules that house 2-mm thick silicon pixel detectors. AXTAR will provide a significant improvement in effective area (a factor of 7 at 4 keV and a factor of 36 at 30 keV) over the RXTE PCA. AXTAR will also carry a sensitive Sky Monitor (SM) that acts as a trigger for pointed observations of X-ray transients in addition to providing high duty cycle monitoring of the X-ray sky. We review the science goals and technical concept for AXTAR and present results from a preliminary mission design study.Comment: 19 pages, 10 figures, to be published in Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, Proceedings of SPIE Volume 773

Design and Analysis for a CubeSat Mission

This project supports the design of a three-unit Cube Satellite (CubeSat) mission pursued by WPI, NASA Goddard Space Flight Center, and the Space Research Centre in Poland. The mission goal is to perform solar and terrestrial X-ray spectroscopy using the Sphinx-NG instrument, in a high-altitude, polar, sun-synchronous orbit. Orbital and radiation analyses are performed using the Satellite Tool Kit. The plasma environment anticipated during the mission is assessed for future charging analysis. The selection and integration of a magnetometer and a GPS sensor are presented. The magnetic fields induced by CubeSat’s three magnetic torquers are obtained using COMSOL and guide the integration of the magnetometer. A preliminary design of the command and data handling subsystem is presented