SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 20 - OCTOBER 07, 2006

19 SPACECRAFT INSTRUMENTATION AND ASTRIONICS
Includes the design, manufacture, or use of devices for the purpose of measuring, detecting, controlling, computing, recording, or processing data related to the operation of space vehicles or platforms.

For related information see also 06 Avionics and Aircraft Instrumentation; for spaceborne instruments not integral to the vehicle itself see 35 Instrumentation and Photography; for spaceborne telescopes and other astronomical instruments see 89 Astronomy.

20050215410 NASA Glenn Research Center, Cleveland, OH, USA

International Space Station Solar Array Wing On-Orbit Electrical Performance Degradation Measured

Gustafson, Eric D.; Kerslake, ThomasW.; Research and Technology 2003; May 2004; 3 pp.; In English; No Copyright;Avail.: CASI: A01, Hardcopy

The port-side photovoltaic power module (P6) was activated on the International Space Station in December 2000. P6 provides electrical power to channels 2B and 4B to operate ISS power loads. A P6 is shown in the preceding photograph. This article highlights the work done at the NASA Glenn Research Center to calculate the on-orbit degradation of the P6 solar array wings (SAWs) using on-orbit data from December 2000 to February 2003. During early ISS operations, the 82 strings of photovoltaic cells that make up a SAW can provide much more power than is necessary to meet the demand. To deal with excess power, a sequential shunt unit successively shunts the current from the strings. This shunt current was the parameter chosen for the SAW performance degradation study for the following reasons: (1) it is based on a direct shunt current measurement in the sequential shunt unit, (2) the shunt current has a low temperature dependence that reduces the data correction error from using a computationally derived array temperature, and (3) the SSU shunt current is essentially the same as the SAW short-circuit current on a per-string basis. Derived from text

International Space Station; Solar Arrays; Performance Tests; Photovoltaic Cells

20050215415 NASA Glenn Research Center, Cleveland, OH, USA

Space Station Power Generation Investigated in Support of the Beta Gimbal Anomaly Resolution

Delleur, Ann M.; Propp, Timothy; Research and Technology 2003; May 2004; 3 pp.; In English; No Copyright; Avail.: CASI: A01, Hardcopy

The International Space Station (ISS) is the largest and most complex spacecraft ever assembled and operated in orbit. The first U.S. photovoltaic module, containing two solar arrays, was launched, installed, and activated in early December 2000. After the first week of continuously rotating the U.S. solar arrays, engineering personnel in the ISS Mission Evaluation Room observed higher than expected electrical currents on the drive motor in one of the Beta Gimbal Assemblies (BGA), the mechanism used to maneuver a U.S. solar array (see the on-orbit photograph). The magnitude of the motor currents continued to increase over time on both BGAs, creating concerns about the ability of the gimbals to continue pointing the solar arrays towards the Sun, a function critical for continued assembly of the ISS. The BGA provides two critical capabilities to the ISS: (1) transfer of electrical power across a rotating joint and (2) positioning of the solar arrays. A number of engineering disciplines convened in May 2001 to address this on-orbit hardware anomaly. Over the course of a year, many scenarios were developed and used. Only two are discussed here: parked arrays and dual-angle mode. Derived from text

Photovoltages; Solar Arrays; Currents

Source: NASA.