SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 16 - AUGUST 12, 2005

06 AVIONICS AND AIRCRAFT INSTRUMENTATION
Includes all avionics systems, cockpit and cabin display devices, and flight instruments intended for use in aircraft.

For related information see also 04 Aircraft Communications and Navigation; 08 Aircraft Stability and Control; 19 Spacecraft Instrumentation and Astrionics; and 35 Instrumentation and Photography.

20050192542 GeoForschungsZentrum, Potsdam, Germany

TIGA: Tide Gauge Benchmark Monitoring Pilot Project

Schoene, Tilo; International GPS Service 2001 - 2002 Technical Reports; September 2004, pp. 361-364; In English; See also 20050192500; Original contains color illustrations; No Copyright; Avail: CASI; A01, Hardcopy; Available from CASI on CD-ROM only as part of the entire parent document

The TIGA Pilot Project was initiated in response to the demanding need for highly precise height coordinates and their changes with time at tide gauge benchmarks. TIGA was formally established during the 16th IGS Governing Board Meeting in Nice (April 2001). For the first time it is not the intention of the IGS to provide results with a very low latency, but to have as many stations included as possible. The primary product of the service is time series of coordinates for analyzing vertical motions of Tide Gauges (TG) and Tide Gauge Benchmarks (TGBM). All products will be made public to support and encourage other applications, e.g. sea level studies. In particular, the products of the service will facilitate the distinction between absolute and relative sea level changes by accounting for the vertical uplift of the station, and are, therefore, an important contribution to climate change studies. The service may further contribute to the calibration of satellite altimeters and other oceanographic activities. The pilot project will operate for a period of three years, from 2001 to 2004. After this period the IGS Governing Board will evaluate the project and decide whether or not this activity should become a regular IGS service function. Derived from text

Measuring Instruments; Time Series Analysis; Coordinates; Vertical Motion

20050192646 NASA Langley Research Center, Hampton, VA, USA

Latency in Visionic Systems: Test Methods and Requirements

Bailey, Randall E.; Arthur, J. J., III; Williams, Steven P.; Kramer, Lynda J.; [2005]; 14 pp.; In English; Workshop on Toward Recommended Methods for Testing and Evaluation of EV and ESV Based Visionic Devices, 26-27 Apr. 2005, Williamsburg, VA, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): 23-079-60-10; No Copyright; Avail: CASI; A03, Hardcopy

A visionics device creates a pictorial representation of the external scene for the pilot. The ultimate objective of these systems may be to electronically generate a form of Visual Meteorological Conditions (VMC) to eliminate weather or time-of-day as an operational constraint and provide enhancement over actual visual conditions where eye-limiting resolution may be a limiting factor. Empirical evidence has shown that the total system delays or latencies including the imaging sensors and display systems, can critically degrade their utility, usability, and acceptability. Definitions and measurement techniques are offered herein as common test and evaluation methods for latency testing in visionics device applications. Based upon available data, very different latency requirements are indicated based upon the piloting task, the role in which the visionics device is used in this task, and the characteristics of the visionics cockpit display device including its resolution, field-of-regard, and field-of-view. The least stringent latency requirements will involve Head-Up Display (HUD) applications, where the visionics imagery provides situational information as a supplement to symbology guidance and command information. Conversely, the visionics system latency requirement for a large field-of-view Head-Worn Display application, providing a Virtual-VMC capability from which the pilot will derive visual guidance, will be the most stringent, having a value as low as 20 msec. Author

Weather; Imaging Techniques; Technology Utilization; Time Lag; Enhanced Vision; Avionics; Head-Up Displays

20050194723 NASA Lewis Research Center, Cleveland, OH, USA

Pyroshock Environments Characterized for Spacecraft Missions

Hughes, William O.; McNelis, Anne M.; Research Technology 1998; April 1999; 3 pp.; In English; Original contains color illustrations; No Copyright; Avail: CASI; A01, Hardcopy

Pyrotechnic shock, or pyroshock, is the transient response of a structure to loading induced by the ignition of pyrotechnic (explosive or propellant activated) devices. These devices are typically used to separate structural systems (e.g., separate a spacecraft from a launch vehicle) and deploy appendages (e.g., solar panels). Pyroshocks are characterized by high peak acceleration, high-frequency content, and short duration. Because of their high acceleration and high-frequency, pyroshocks can cause spaceflight hardware to fail.

Verifying by test that spaceflight hardware can withstand the anticipated shock environment is considered essential to mission success. The Earth Observing System (EOS) AM-1 spacecraft for NASA’s Mission to Planet Earth is scheduled to be launched on an Atlas IIAS vehicle in 1999, and the NASA Lewis Research Center is the launch vehicle integrator for this NASA Goddard Space Flight Center spacecraft. The EOS spacecraft was subjected to numerous ground shock tests to verify that its scientific instruments and avionics components will withstand the shock-induced vibration produced when the spacecraft separates from the launch vehicle.

Shock test data from these tests represent the third largest available pyroshock database in the USA. Future spacecraft missions will directly benefit from the knowledge gained from these tests.

The payload separation system used for EOS is a new system that operates by firing six separation nuts. This system was tested to verify its functional operation and to characterize the resulting shock levels. The launch vehicle contractor (Lockheed Martin Astronautics) and spacecraft contractor (Lockheed Martin Missiles & Space) completed 16 separation test firings. This resulted in an unusually large amount of pyroshock data.

Typically, only one or two pyroshock test firings are performed for a spacecraft mission. Because of the size of this separation system shock database, engineers were able to perform unique statistical analyses to characterize the distribution of the test data. For example, it was proven that the shock data follow a lognormal distribution, a concept often assumed but rarely proven. The test-to-test repeatability of the shock source level was analyzed, and the effects of various test configurations and separation nut production lots were examined and quantified.

Engineers investigated the change in shock level as the shock traveled from the spacecraft separation interface to the avionics components of the upper stage and analyzed the effects of the structural fidelity (simulator versus real) of the components and their weight on vibrational response. In addition, the shock attenuation with distance and across joints was quantified and compared with concepts originally generated in 1970, and the effects of separation nut preload and firing sequences effects were examined.

Because of this EOS shock testing and the analyses performed at NASA Lewis, a significant amount of new information on pyroshock and its characteristics is now available to the aerospace industry. We hope that this information will help future spacecraft test planners to perform better and cheaper spacecraft separation shock tests and to better understand their test data. Author

Pyrotechnics; Shock Tests; Space Missions; Avionics; Launch Vehicles

Source: NASA.