The CALTRACÃ‚Â® star tracker is a space-borne attitude sensor, that uses a wide-angle all-reflective telescope with a highly curved image surface and a small f-number. There are a number of critical optical metrology activities that are involved in building the star tracker. These include, among others, aligning the optics and CCD detector subassemblies to form an optics head by using a five-star simulator, measuring angles between internal optical axes and external references for space-craft integration, positioning the vertex of the optics to the rotation axis of a 2D rotary table for subsequent optical calibrations, determining the lateral location of an internal CCD baffle, and verifying the precision of the 2D rotary table to arc- second accuracy. Optical measurements involved in these activities must be performed accurately, so as to ensure the overall performance of the integrated star tracker system. This paper is intended to introduce the methods of optical measurement that were developed for these purposes. Accuracy achieved with these methods has proven sufficient in supporting the development and production of the star trackers.
To date there have not been any direct measurements of winds in the Martian atmosphere. Measurements such as these are needed in order to understand the nature of the circulation and the transport of constituents in the atmosphere of this planet. In this paper, a conceptual design for a small visible/near-IR imaging interferometer capable of fulfilling this need is described. The design is based on a similar successful instrument, the Wind Imaging Interferometer (WINDII), which flew in Earth orbit. The basic measurement set includes Doppler shifts (from which wind is derived), rotational temperatures, line widths and radiances of isolated lines in the O2(α1Δg) band airglow and O(1S) airglow emission. The design challenges which were met in converting an instrument designed for terrestrial applications to one capable of flying to Mars and operating in conditions there include reducing the mass and power requirements and adapting the instrument to appropriate data rate and S/N requirements. The resulting instrument has a mass of approximately 15 kg, requires on average, 10 Watts of power and has a data rate of 32Mbits/day. In this paper the design of this instrument and how it accommodates the particular requirements of a Mars mission are described.
SWIFT is a small (< 85 kg, approximately 0.5 m3, < 100 W) satellite instrument which is designed to accurately measure global horizontal winds and ozone concentrations in the stratosphere. SWIFT is similar to the highly successful WINDII instrument currently operating on the UARS satellite. Both use a field-widened Michelson interferometer set at high path difference to image the Doppler shift of atmospheric emission. The data set provided by SWIFT will provide essential input to the next generation of Numerical Weather Prediction (NWP) models which are currently being developed by meteorological organizations worldwide. SWIFT is currently a leading candidate to fill the foreign instrument opening for the NASDA GCOM-A1 mission, providing highly complimentary data to the ODUS and SOFIS instruments. SWIFT allows direct measurement of stratospheric dynamics and high vertical resolution ozone profiling to maximize the scientific return for this mission.