A Technology Study for Free-Flying Sciencecraft, 15-9198

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Principal Investigators
 Raymond Goldstein
James P. Cravens
Jerry A. Helffrich
Mark B. Tapley
Bill Tomlinson

Inclusive Dates: 07/01/00 - Current

Background - Each of the four free-flying magnetometers (FFMs) deployed from a suborbital rocket in previous work was an 8-centimeter diameter by 3.8-centimeter high cylinder. They each carried a three-axis fluxgate magnetometer, electronics, primary power, and telemetry system, with a total mass of 250 grams. The FFMs successfully measured the magnetic field in the northern auroral region during the 15-minute flight and telemetered the results to the ground station. This mission served as a proof-of-concept for the FFMs. Considerable development is still needed for their application to longer missions such as orbiting Earth or other planets. In addition, the possibility of incorporating other instruments such as particle sensors in the FFMs is envisioned. Miniaturization of all subsystems is critical for such highly integrated sciencecraft. In particular, SwRI needs to develop devices and techniques to determine the sciencecraft attitude and position if the FFMs are to be useful for longer missions such as in Earth orbit.

Approach - The study involves understanding current state-of-the-art capability and the advancements necessary for developing miniaturized attitude and position determination systems. The research team will then develop a system concept and packaging design to allow incorporation into a nano-sciencecraft.

Accomplishments - The team has assembled and tested a miniaturized Sun sensor in a "nano-craft" mockup. The illustration of the 10-centimeter diameter mockup below shows the electronics board that runs the detector, which is directly in front of the board. The 0.5-millimeter aperture that views the Sun is located at the end of the short tube projecting into the page. The detector is a 1-centimeter by 1-centimeter two-dimensional silicon device. For some of the tests, the mockup was mounted on a rotary table, which allows simulation of a spinning sciencecraft rotating through the Sun's image.

The spin-phase angle determination involves modeling the zero crossings of the difference between the left and right signals, while the elevation angle of the Sun is determined by the difference between the top and bottom detector signals. Tests to date show that this technique easily allows a 0.01° spin angle as well as an elevation angle determination.

Mockup of SwRI-developed miniaturized Sun-sensor

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