Shuttle derived atmospheric density model. Part 2: STS atmospheric implications for AOTV trajectory analysis, a proposed GRAM perturbation density model

A perturbation model to the Marshall Space Flight Center (MSFC) Global Reference Atmosphere Model (GRAM) was developed for use in the Aeroassist Orbital Transfer Vehicle (AOTV) trajectory and analysis. The model reflects NASA Space Shuttle experience over the first twelve entry flights. The GRAM was selected over the Air Force 1978 Reference Model because of its more general formulation and wider use throughout NASA. The add-on model, a simple scaling with altitude to reflect density structure encountered by the Shuttle Orbiter was selected principally to simplify implementation. Perturbations, by season, can be utilized to minimize the number of required simulations, however, exact Shuttle flight history can be exercised using the same model if desired. Such a perturbation model, though not meteorologically motivated, enables inclusion of High Resolution Accelerometer Package (HiRAP) results in the thermosphere. Provision is made to incorporate differing perturbations during the AOTV entry and exit phases of the aero-asist maneuver to account for trajectory displacement (geographic) along the ground track

Shuttle derived atmospheric density model. Part 1: Comparisons of the various ambient atmospheric source data with derived parameters from the first twelve STS entry flights, a data package for AOTV atmospheric development

The ambient atmospheric parameter comparisons versus derived values from the first twelve Space Shuttle Orbiter entry flights are presented. Available flights, flight data products, and data sources utilized are reviewed. Comparisons are presented based on remote meteorological measurements as well as two comprehensive models which incorporate latitudinal and seasonal effects. These are the Air Force 1978 Reference Atmosphere and the Marshall Space Flight Center Global Reference Model (GRAM). Atmospheric structure sensible in the Shuttle flight data is shown and discussed. A model for consideration in Aero-assisted Orbital Transfer Vehicle (AOTV) trajectory analysis, proposed to modify the GRAM data to emulate Shuttle experiments

Paper Session II-A - Lunar Vehicle Assembly and Processing on Space Station Freedom

Space Station Freedom has been designed with the capability to evolve in functionality and size. A likely direction for Freedom evolution will be toward the establishment of a Low Earth Orbit (LEO) transportation node for solar system exploration vehicles. The Human Exploration Initiative proposed by President Bush in July of 1989 takes advantage of Freedom\u27s evolutionary nature by utilizing Freedom\u27s on orbit resources for the assembly, check-out and refurbishment of lunar and Mars transfer vehicles. This paper discusses a concept for accommodating lunar vehicles on Space Station Freedom. Lunar vehicle processing requirements and their associated impacts on Freedom are evaluated with respect to need for additional crew, EVA, power and thermal rejection capability. A preliminary definition of a lunar vehicle processing facility is described and an assessment is made of support equipment required in the facility to accomplish the processing tasks. Additional resource requirements coupled with the need for new structure and the lunar vehicle processing facility, induce a major change in the physical characteristics of Freedom. Mass properties, microgravity environment, flight attitude, controllability and reboost fuel requirements are all evaluated to assess the impact on Freedom of accommodating the massive lunar transportation vehicles. The results of the above analysis indicate that Freedom can evolve into a highly capable lunar transportation node with respect to accommodating the assembly of vehicles, fuel tanks and aerobrakes, the check-out and validation of the assembled vehicles and their associated subsystems, and the refurbishment of these same vehicles after a mission has been completed

Trajectory reconstruction and aerodynamic results from the first Discovery flight, STS-14(41-D)

Trajectory reconstruction results for the first Discovery flight are presented. Spacecraft dynamic measurements from IMU2 were utilized in conjunction with the ground based tracking data from two S-band stations, eight C-band, and five cameras at Edwards Air Force Base to determine the spacecraft trajectory from epoch through roll-out on Runway 17. Specifics as to the trajectory reconstruction are discussed in Section 1. The final inertial profile is BT14NO2/UN=169750N. Merging of this file with the final LAIRS atmosphere is discussed in Section 2. The final Extended BET is ST14BET/UN=274885C. Section 3 presents plots of relevant parameters from the AEROBET as well as aerodynamic performance comparison results. High frequency files for maneuver extraction were also generated as discussed in Section 4. Appendices are attached which contain: (1) spacecraft and physical parameters utilized, (2) final residuals obtained from the data fitting process, (3) listing of trajectory parameters, and (4) archival information

Challenger STS-17 (41-G) post-flight best estimate trajectory products: Development and summary results

Results from the STS-17 (41-G) post-flight products are presented. Operational Instrumentation recorder gaps, coupled with the limited tracking coverage available for this high inclination entry profile, necessitated selection of an anchor epoch for reconstruction corresponding to an unusually low altitude of h approx. 297 kft. The final inertial trajectory obtained, BT17N26/UN=169750N, is discussed in Section I, i.e., relative to the problems encountered with the OI and ACIP recorded data on this Challenger flight. Atmospheric selection, again in view of the ground track displacement from the remote meteorological sites, constituted a major problem area as discussed in Section II. The LAIRS file provided by Langley was adopted, with NOAA data utilized over the lowermost approx. 7 kft. As discussed in Section II, the Extended BET, ST17BET/UN=274885C, suggests a limited upper altitude (H approx. 230 kft) for which meaningful flight extraction can be expected. This is further demonstrated, though not considered a limitation, in Section III wherein summary results from the AEROBET (NJ0333 with NJ0346 as duplicate) are presented. GTFILEs were generated only for the selected IMU (IMU2) and the Rate Gyro Assembly/Accelerometer Assembly data due to the loss of ACIP data. Appendices attached present inputs for the generation of the post-flight products (Appendix A), final residual plots (Appendix B), a two second spaced listing of the relevant parameters from the Extended BET (Appendix C), and an archival section (Appendix D) devoting input (source) and output files and/or physical reels

Post-flight BET products for the 2nd discovery entry, STS-19 (51-A)

The post-flight products for the second Discovery flight, STS-19 (51-A), are summarized. The inertial best estimate trajectory (BET), BT19D19/UN=169750N, was developed using spacecraft dynamic measurements from Inertial Measurement Unit 2 (IMU2) in conjunction with the best tracking coverage available for any of the earlier Shuttle entries. As a consequence of the latter, an anchor epoch was selected which conforms to an initial altitude of greater than a million feet. The Extended BET, ST19BET/UN=274885C, incorporated the previously mentioned inertial reconstructed state information and the Langley Atmospheric Information Retrieval System (LAIRS) atmosphere, ST19MET/UN=712662N, with some minor exceptions. Primary and back-up AEROBET reels are NK0165 and NK0201, respectively. This product was only developed over the lowermost 360 kft altitude range due to atmosphere problems but this relates to altitudes well above meaningful signal in the IMUs. Summary results generated from the AEROBET for this flight are presented with meaningful configuration and statistical comparisons from the previous thirteen flights. Modified maximum likelihood estimation (MMLE) files were generated based on IMU2 and the Rate Gyro Assembly/Accelerometer Assembly (RGA/AA), respectively. Appendices attached define spacecraft and physical constants utilized, show plots of the final tracking data residuals from the post-flight fit, list relevant parameters from the BET at a two second spacing, and retain for archival purpose all relevant input and output tapes and files generated

Affinity and dose of TCR engagement yield proportional enhancer and gene activity in CD4+ T cells.

Affinity and dose of T cell receptor (TCR) interaction with antigens govern the magnitude of CD4+ T cell responses, but questions remain regarding the quantitative translation of TCR engagement into downstream signals. We find that while the response of mouse CD4+ T cells to antigenic stimulation is bimodal, activated cells exhibit analog responses proportional to signal strength. Gene expression output reflects TCR signal strength, providing a signature of T cell activation. Expression changes rely on a pre-established enhancer landscape and quantitative acetylation at AP-1 binding sites. Finally, we show that graded expression of activation genes depends on ERK pathway activation, suggesting that an ERK-AP-1 axis plays an important role in translating TCR signal strength into proportional activation of enhancers and genes essential for T cell function

Development and fabrication of a fast recovery, high voltage power diode

The use of positive bevels for P-I-N mesa structures to achieve high voltages is described. The technique of glass passivation for mesa structures is described. The utilization of high energy radiation to control the lifetime of carriers in silicon is reported as a means to achieve fast recovery times. Characterization data is reported and is in agreement with design concepts developed for power diodes

Isoperimetric inequalities for some integral operators arising in potential theory

In this paper we review our previous isoperimetric results for the logarithmic potential and Newton potential operators. The main reason why the results are useful, beyond the intrinsic interest of geometric extremum problems, is that they produce a priori bounds for spectral invariants of operators on arbitrary domains. We demonstrate these in explicit examples.Comment: This conference paper gives a review of our previous results in the subjec

Harry Reid Center of Environmental Studies: Quality assurance program evaluation

The Quality Assurance (QA) Program is critical in the licensing of the Yucca Mountain Repository because it helps ensure that the information used to demonstrate the safer)\u27 of the repository is defensible and well documented. Through audits and surveillances the QA staff identifies areas of non-compliance within each task. The QA Program at the Harry Reid Center (HRC) for Environmental Studies can increase compliance with Quality /Assurance Procedures (QAPs) by improving the program\u27s process. Through qualitative and quantitative research it was determined that reasons for non-compliance revolved around three key areas; process, communication and training. Communication and training are key components of the process for ensuring compliance. Therefore, our recommendations focus on process improvements. This evaluation contains recommendations related to improving processes within the QA Program. In particular, the QA Program should enhance its current training program by making it more hands on, utilising pre/post-tests, requiring mandatory annual training, creating an easy to use reference manual and hiring a full time trainer. In addition, communication can be improved by increasing the number of meetings between Pis and researchers, having mandatory regularly scheduled meetings with QA staff in the Reno area, and creating and maintaining a database for all statt associated with every task. Finally, the QA Program should create incentives for compliance and consequences for noncompliance