Shuttle Payload Bay Research Articles

The Shuttle Radar Topography Mission—A New Source of Near-Global Digital Elevation Data

The Shuttle Radar Topography Mission (SRTM) has generated a homogeneous near-global digital elevation model (DEM) of the Earth using single-pass radar interferometry. The crew of Space Shuttle Endeavour (STS-99) operated the modified dual-antenna synthetic aperture radar systems for 11 days in February 2000. SRTM acquired both C-band and X-band synthetic aperture radar data, collecting 3D data using a 60-metre mast extending from the shuttle payload bay, containing additional C-band and X-band receiver antennas.SRTM DEM data have a horizontal resolution of 1 arc second (30 m at the equator) and vertical resolution of 10 m (C-band radar). SRTM-1 (1 arc second) data are available for US territories only, with subsampled SRTM-3 (3 arc second) data provided for the rest of the world. The USGS is responsible for archiving the data, with 3 arc second data being made freely available on a continent-by-continent basis. All data processing was completed in July 2004. Comparison of SRTM DEM data with older GTOPO and altimetric DEMs shows a significant improvement in horizontal and/or vertical resolution, similar to that achieved by ASTER. The SRTM DEM data provide a useful new resource, especially in areas where limited topographic data are available.

The Shuttle Radar Topography Mission–a new source of near-global digital elevation data

The Shuttle Radar Topography Mission (SRTM) has generated a homogeneous near-global digital elevation model (DEM) of the Earth using single-pass radar interferometry. The crew of Space Shuttle Endeavour (STS-99) operated the modified dual-antenna synthetic aperture radar systems for 11 days in February 2000. SRTM acquired both C-band and X-band synthetic aperture radar data, collecting 3D data using a 60-metre mast extending from the shuttle payload bay, containing additional C-band and X-band receiver antennas. SRTM DEM data have a horizontal resolution of 1 arc second (30 m at the equator) and vertical resolution of 10 m (C-band radar). SRTM-1 (1 arc second) data are available for US territories only, with subsampled SRTM-3 (3 arc second) data provided for the rest of the world. The USGS is responsible for archiving the data, with 3 arc second data being made freely available on a continent-by-continent basis. All data processing was completed in July 2004. Comparison of SRTM DEM data with older GTOPO and altimetric DEMs shows a significant improvement in horizontal and/or vertical resolution, similar to that achieved by ASTER. The SRTM DEM data provide a useful new resource, especially in areas where limited topographic data are available.

Negative pickup ions detected during the TSS 1 mission

We report the occasional detection of negative pickup ions by the Shuttle Potential and Return Electron Experiment (SPREE) in the shuttle payload bay during the first Tethered Satellite System (TSS 1) mission. These ions appear as arch‐like structures of enhanced fluxes in energy versus time spectrograms for the SPREE electron zone looking in the plane perpendicular to the Earth's magnetic field. Maximum energies of ∼56 eV were measured when the sensor looked closest to the shuttle ram direction. Empirically, the energy of associated spectral peaks decreases as cos2 ξ, where ξ is the angle between the sensor look direction and the projection of the shuttle's velocity onto the plane perpendicular to the magnetic field. These signatures may be found under day or night conditions and always in conjunction with positively charged pickup ions generated as a result of firings by the L5D and/or R5D vernier thrusters. We show that positive ion contamination and accelerated electrons cannot be the responsible agents. Observed spectral characteristics are most easily explained as either NO2− or MMH− ions created near the shuttle and accelerated by the motional electric field to energies detectable by SPREE.

Thruster effects on the shuttle potential during TSS 1

We have surveyed measurements taken by the Shuttle Potential and Return Electron Experiment (SPREE) in the shuttle payload bay during the satellite deployment phase of the Tethered Satellite System (TSS 1) mission. The shuttle was flying in an inverse airplane mode with its engine bells facing the ram direction to facilitate ion current collection. SPREE ion spectral measurements indicate that with no thrusters firing, the shuttle charged to, at most, a few tens of volts negative. We identified 13 intervals during which the tether was electrically connected to the shuttle by a low‐impedance shunt and thruster firings occurred. In previously reported examples of neutral gas releases from charged spacecraft the magnitude of the vehicle potential decreased. Thruster firings during our events either left the TSS circuit unchanged or caused the current measured in the tether to diminish and the shuttle to become more negatively charged. In the latter case it appears that thruster gas impeded access of ambient ions to the current collecting surfaces of the shuttle. The changes in the distribution of the motionally induced potential between the tether and sheath calculated using Ohm's law are in agreement with SPREE measurements.

Measurements on the Shuttle of the LET Spectra of Galactic Cosmic Radiation and Comparison with the Radiation Transport Model

A new class of tissue-equivalent proportional counters has been flown on two space shuttle flights. These detectors and their associated electronics cover a lineal energy range from 0.4 to 1250 keV/microns with a multichannel analyzer resolution of 0.1 keV/microns from 0.4 to 20 keV/microns and 5 keV/microns from 20 to 1250 keV/microns. These detectors provide the most complete dynamic range and highest resolution of any technique currently in use. On one mission, one detector was mounted in the Shuttle payload bay and another older model in the mid-deck, thus providing information on the depth dependence of the lineal energy spectrum. A detailed comparison of the observed lineal energy and calculated LET spectra for galactic cosmic radiation shows that, although the radiation transport models provide a rather accurate description of the dose (+/- 15%) and equivalent dose (+/- 15%), the calculations significantly underestimate the frequency of events below about 100 keV/microns. This difference cannot be explained by the inclusion of the contribution of splash protons. The contribution of the secondary pions, kaons and electrons produced in the Shuttle shielding, if included in the radiation transport model, may explain these differences. There are also significant differences between the model predictions and observations above 140 keV/microns, particularly for 28.5 degrees inclination orbit.

A Cloud-to-Space Lightning as Recorded by the Space Shuttle Payload-Bay TV Cameras

A Cloud-to-Space Lightning as Recorded by the Space Shuttle Payload-Bay TV Cameras

Orbital maneuvering vehicle: A new capability

The Orbital Maneuvering Vehicle (OMV) is a reusable, remotely controlled, free-flying vehicle being developed by NASA to perform a wide range of on-orbit missions and services in support of orbiting spacecraft. The OMV is capable of satellite delivery, retrieval, reboost, controlled deorbit, viewing, and subsatellite support missions. It is an important extension to the Space Transportation System and a key element of the Space Station operational scenario. The OMV can operate from the Shuttle, the Space Station, or can be space based. The OMV, being 15 ft in diameter and approximately 4 1 2 thick, mounts directly into the Shuttle payload bay. The vehicle design is highly modular, consisting of a Short Range Vehicle containing both hydrazine and cold gas RCS systems and all the avionics systems for electrical power, communications, data management, guidance, navigation, and 6-degree of freedom control. This vehicle weighs approximately 6,500 lb and can accomplish a high percentage of the project missions. For high delta-velocity missions, a bipropellant Propulsion Module (approximately 11,000lb) is added, giving a total weight of 17,500 lb. This module can be exchanged on orbit to effect bipropellant refueling. All the RCS and avionics modules are replaceable on orbit for maintenance. The OMV development program was initiated in 1986 with the selection of TRW as the prime contractor. The first flight is projected for 1991. An early planned use of OMV is to reboost the Hubble Space Telescope when required because of atmospheric drag. This paper contains details of the program status, vehicle description, and mission capabilities. The purpose of the paper is to acquaint the international space community with OMV capabilities and to stimulate the identification of new and unique mission applications.

Science and technology results from the OSS-1 payload on the Space Shuttle

The OSS-1 Payload of nine experiments was carried on the STS-3 Space Shuttle flight in March of 1982. The OSS-1 Payload contained four instruments that evaluated specific aspects of the Orbiter's environment, including the levels of particulate, gaseous and electromagnetic emissions given off by the Orbiter, and the interactions between the Orbiter and the surrounding plasma. In addition to these environmental observations, these instruments performed scientific investigations in astronomy and in space plasma physics, including active experiments in electron beam propagation. Other experiments were in the areas of solar physics, plant growth, micrometeorite studies and the technology of actively controlled heat pipes. We present the initial results from these experiments, with some implications of these results for future operation of space experiments from the Shuttle payload bay. One major result was the unexpected discovery of a faint surface-induced optical glow created near the Shuttle surfaces by impacts of ambient atmospheric atoms and molecules.

Specular effects of Shuttle Orbiter radiators on a typical payload

Analyses performed to determine the Space Shuttle's payload bay thermal environment generally consider all external surfaces of the Orbiter and its payload to reflect energy diffusely. However, the Orbiter's active thermal control system (ATCS) radiators util ize highly specular silverized Teflon on their outer surfaces. This study considers solar energy specularly reflected from these radiators on a typical deployed payload which extends outside the paySoad bay envelope. Parameters investigated include the degree of specularity of the radiators and the solar inclination angle with respect to the radiators. Comparisons are made between payload environmental heat flux levels assuming both diffuse and specular radiators.

Optimization using sensitivity analysis

T paper describes a general sensitivity analysis and design optimization approach. The approach is presented by example as used in optimizing the structural shell used for the airborne support equipment which supports the inertial upper stage in the Space Shuttle (orbiter) payload bay. The paper illustrates that major improvements in design can be made with a simplified sensitivity analysis.

Prediction of the Acoustic Environment in the Space Shuttle Payload Bay

An analytical model has been developed to predict space-averaged sound levels in the payload bay of the Space Shuttle when the bay is empty or when a payload is present. The model utilizes the power flow concept and takes into account net power flow from the exterior, flow between subvolumes surrounding a payload, and power dissipation in the subvolumes. The characteristics of the model are described and its application to the Spacelab Configuration 1 payload is presented to illustrate the type of results obtained.