Engineering topics

Seacord, A. W., II

Publications and source records attributed to Seacord, A. W., II.

4 records

NASA NTRS1992

Double lunar swingby and Lissajous trajectory design for the WIND mission

Two alternative mission profiles are presented for the WIND mission whose baseline design includes two years in a double lunar swingby (DLS) orbit followed by one year in a Lissajous orbit about the sun-earth L1 libration point. The first alternative uses a half-month high-inclination transfer orbit between two lunar gravity assists to change the initial sunward DLS orbit to a DLS orbit in the geomagnetic tail region. The second alternative uses a direct insertion from launch into a large-amplitude Lissajous orbit followed by a sunward DLS orbit.

Sharer, P. J.↗

NASA NTRS1992

Transfer trajectory design for the SOHO libration-point mission

It is shown that transfer trajectories to the halo orbit exist throughout the year, with a one week closure of the launch window each month because of unfavorable lunar perturbations that cannot be corrected in the case of transfer trajectory insertion errors. The launch window for transfers to large-amplitude Lissajous orbits is virtually the same as that for transfers to the baseline halo orbit. Details of these trajectories are described and questions about groundstation coverage are discussed.

Dunham, D. W.↗

NASA NTRS1986

Ascent/descent ancillary data production user's guide

The Ascent/Descent Ancillary Data Product, also called the A/D BET because it contains a Best Estimate of the Trajectory (BET), is a collection of trajectory, attitude, and atmospheric related parameters computed for the ascent and descent phases of each Shuttle Mission. These computations are executed shortly after the event in a post-flight environment. A collection of several routines including some stand-alone routines constitute what is called the Ascent/Descent Ancillary Data Production Program. A User's Guide for that program is given. It is intended to provide the reader with all the information necessary to generate an Ascent or a Descent Ancillary Data Product. It includes descriptions of the input data and output data for each routine, and contains explicit instructions on how to run each routine. A description of the final output product is given.

Brans, H. R.↗

NASA NTRS1986

Engineering description of the ascent/descent bet product

The Ascent/Descent output product is produced in the OPIP routine from three files which constitute its input. One of these, OPIP.IN, contains mission specific parameters. Meteorological data, such as atmospheric wind velocities, temperatures, and density, are obtained from the second file, the Corrected Meteorological Data File (METDATA). The third file is the TRJATTDATA file which contains the time-tagged state vectors that combine trajectory information from the Best Estimate of Trajectory (BET) filter, LBRET5, and Best Estimate of Attitude (BEA) derived from IMU telemetry. Each term in the two output data files (BETDATA and the Navigation Block, or NAVBLK) are defined. The description of the BETDATA file includes an outline of the algorithm used to calculate each term. To facilitate describing the algorithms, a nomenclature is defined. The description of the nomenclature includes a definition of the coordinate systems used. The NAVBLK file contains navigation input parameters. Each term in NAVBLK is defined and its source is listed. The production of NAVBLK requires only two computational algorithms. These two algorithms, which compute the terms DELTA and RSUBO, are described. Finally, the distribution of data in the NAVBLK records is listed.

Seacord, A. W., II↗