Optical alignment of the Global Precipitation Measurements (GPM) star trackers

Samuel Hetherington; Dean Osgood; Joe McMann; Viki Roberts; James Gill; Kyle McLean

doi:10.1117/12.2024558

10 September 2013 Optical alignment of the Global Precipitation Measurements (GPM) star trackers

Samuel Hetherington, Dean Osgood, Joe McMann, Viki Roberts, James Gill, Kyle McLean

Proceedings Volume 8844, Optical System Alignment, Tolerancing, and Verification VII; 884406 (2013) https://doi.org/10.1117/12.2024558
Event: SPIE Optical Engineering + Applications, 2013, San Diego, California, United States

Abstract

The optical alignment of the star trackers on the Global Precipitation Measurement (GPM) core spacecraft at NASA Goddard Space Flight Center (GSFC) was challenging due to the layout and structural design of the GPM Lower Bus Structure (LBS) in which the star trackers are mounted as well as the presence of the star tracker shades that blocked line-of-sight to the primary star tracker optical references. The initial solution was to negotiate minor changes in the original LBS design to allow for the installation of a removable item of ground support equipment (GSE) that could be installed whenever measurements of the star tracker optical references were needed. However, this GSE could only be used to measure secondary optical reference cube faces not used by the star tracker vendor to obtain the relationship information and matrix transformations necessary to determine star tracker alignment. Unfortunately, due to unexpectedly large orthogonality errors between the measured secondary adjacent cube faces and the lack of cube calibration data, we required a method that could be used to measure the same reference cube faces as originally measured by the vendor. We describe an alternative technique to theodolite autocollimation for measurement of an optical reference mirror pointing direction when normal incidence measurements are not possible. This technique was used to successfully align the GPM star trackers and has been used on a number of other NASA flight projects. We also discuss alignment theory as well as a GSFC-developed theodolite data analysis package used to analyze angular metrology data.

Citation Download Citation

Samuel Hetherington, Dean Osgood, Joe McMann, Viki Roberts, James Gill, and Kyle McLean "Optical alignment of the Global Precipitation Measurements (GPM) star trackers", Proc. SPIE 8844, Optical System Alignment, Tolerancing, and Verification VII, 884406 (10 September 2013); https://doi.org/10.1117/12.2024558

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available