Early Communication System (ECOMM) for ISS

The International Space Station (ISS) Early Communications System (ECOMM) was a Johnson Space Center (JSC) Avionic Systems Division (ASD) in-house developed communication system to provide early communications between the ISS and the Mission Control Center-Houston (MCC-H). This system allows for low rate commands (link rate of 6 kbps) to be transmitted through the Tracking and Data Relay Satellite System (TDRSS) from MCC-H to the ISS using TDRSS's S-band Single Access Forward (SSA/) link service. This system also allows for low rate telemetry (link rate of 20.48 kbps) to be transmitted from ISS to MCC-H through the TDRSS using TDRSS's S-band Single Access Return (SSAR) link service. In addition this system supports a JSC developed Onboard Communications Adapter (OCA) that allows for a two-way data exchange of 128 kbps between MCC-H and the ISS through TDRSS. This OCA data can be digital video/audio (two-way videoconference), and/or file transfers, and/or "white board". The key components of the system, the data formats used by the system to insure compatibility with the future ISS S-Band System, as well as how other vehicles may be able to use this system for their needs are discussed in this paper

Space-to-Space Communications System

The Space-to-Space Communications System (SSCS) is an Ultra High Frequency (UHF) Time-Division-Multiple Access (TDMA) system that is designed, developed, and deployed by the NASA Johnson Space Center (JSC) to provide voice, commands, telemetry and data services in close proximity among three space elements: International Space Station (ISS), Space Shuttle Orbiter, and Extravehicular Mobility Units (EMU). The SSCS consists of a family of three radios which are, Space-to-Space Station Radio (SSSR), Space-to-Space Orbiter Radio (SSOR), and Space-to-Space Extravehicular Mobility Radio (SSER). The SSCS can support up to five such radios at a time. Each user has its own time slot within which to transmit voice and data. Continuous Phase Frequency Shift Keying (CPFSK) carrier modulation with a burst data rate of 695 kbps and a frequency deviation of 486.5 kHz is employed by the system. Reed-Solomon (R-S) coding is also adopted to ensure data quality. In this paper, the SSCS system requirements, operational scenario, detailed system architecture and parameters, link acquisition strategy, and link performance analysis will be presented and discusse

The effects of bandlimiting on the performance of digital communication systems

The effects of bandlimiting on the performance of various digital transmission systems corrupted by additive white Gaussian noise are analyzed using two methods, the averaging method and the series expansion method. The results from both methods agree. The performance of an ideal bandlimited NRZ (Non-Return- to-Zero) baseband transmission system is examined using correlation detection and sampling. The explicit expression for the degradation of the signal and the intersymbol interference as a function of system parameters is derived. The average, lower bounds and upper bounds of the probabilities of bit-error are computed for both detectors. It is shown that the correlation detector performs better than the sample detector for BT>0.6 and worse for BT=0.5. A Split-Phase baseband system is also analyzed following the same steps used for analyzing the NRZ system. It is shown that a Split-Phase baseband system requires less than twice as much bandwidth as the NRZ system to have the same probability of bit-error for the same value of signal- to-noise ratio using the correlation detector. An NRZ baseband system using Gaussian filters is also analyzed employing correlation detection. It is found that the system introduces more intersymbol interference and performs poorly compared to the ideal bandlimited NRZ system. The effects of bandlimiting on the performance of modulation the Phase-Shift-Keying (PSK) System, the Amplitude-Shift-Keying (ASK) System, and the Frequency-Shift-Keying (FSK) System are analyzed assuming a correlation receiver and using ideal filters as well as correlation detection. The explicit expression for the degradation of the signal and the intersymbol interference as a function of bandwidths of the filters, signal-to-noise ratio and carrier frequencies is given. It is found that the aliasing effect can be neglected if the carrier frequency is more than three times the bit rate. It is also found that PSK requires 3 db less on an average power basis than ASK. If the spacing between the two carrier tones in FSK is less than three times the bit rate, FSK shows a better performance than that of ASK. The optimum setting of the tone spacing of FSK is shown to be equal to the bit rate. However, PSK always gives the best performance. Thus for a coherent system, PSK should always be used. Finally, a tapped-delay-line (TDL) filter is introduced at the receiver of the NRZ baseband system in conjunction with the correlation detector as an intersymbol eliminator. On an average probability of bit-error basis, and using only three taps, it is demonstrated that the performance of this system is near optimum.Electrical and Computer Engineering, Department o

Space Shuttle Payloads and Data-Handling Accommodations

International Telemetering Conference Proceedings / November 19-21, 1979 / Town and Country Hotel, San Diego, CaliforniaThe primary objective of the Space Shuttle Program is to provide an economical space transportation system that will support a wide range of scientific, defense, and commercial applications in Earth orbit. The Shuttle will be a manned, reusable space vehicle designed to accommodate these applications. The advent of the Space Shuttle will usher in an era of space industrialization and utilization which undoubtedly will result in new products, new services, and new sources of energy.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection

Impact Speed Does Not Determine Severity of Spinal Cord Injury in Mice with Fixed Impact Displacement

The speed of three leading rodent SCI impacting devices—0.1 m/s (Infinite Horizon), 0.2 m/s (Ohio State University), and 0.4 m/s (New York University)—were investigated using a custom-fabricated impactor to determine its effect on mouse spinal cord injury severity. The spared white matter was examined at 7 and 21 days post-injury with in vivo diffusion tensor imaging (DTI) and post-mortem histology, respectively. The neurological outcome of the injured mice was longitudinally evaluated using the Basso mouse scale. In vivo DTI derived diffusion anisotropy maps provided excellent gray-white matter contrast enabling objective and noninvasive quantification of normal appearing white matter. In vivo DTI estimated spared white matter content correlated well with those determined using post-mortem histology. No significant difference in BMS was observed among injury groups of various impact speeds. The present results suggest that injury severity can be reproduced using speeds from 0.1 to 0.4 m/s at the fixed impact displacement

Statin use and the risk of chronic kidney disease in patients with psoriasis: A nationwide cohort study in Taiwan.

BackgroundPsoriasis is associated with hyperlipidemia. Few studies have examined the association among psoriasis, hyperlipidemia, and chronic kidney disease (CKD). It remains a topic of debate whether statin treatment for hyperlipidemia prevents the development of CKD in patients with psoriasis.ObjectiveWe investigated whether there is an association among psoriasis, hyperlipidemia and CKD. If so, we asked whether statin treatment for hyperlipidemia reduces the risk of CKD in patients with psoriasis.MethodsA Taiwan nationwide population-based cohort study between 1997 and 2010 included 2,912 patients with psoriasis and 8,736 matched patients without psoriasis (1:3 propensity score matched according to age, sex, and region); 104,609 patients without psoriasis but with hyperlipidemia and 104,609 matched patients without psoriasis or hyperlipidemia (1:1). The hazard ratios, relative risks, and 95% confidence intervals were calculated using Cox proportional hazards model.ResultsPsoriasis significantly increased the risk of CKD (adjusted hazard ratio 2.48, 95% confidence interval 1.81-3.40), and so did hyperlipidemia (adjusted hazard ratio 2.93, 95% confidence interval 2.79-3.08). Compared to treatment without statins, statin treatment for hyperlipidemia reduced the risk of CKD in patients with psoriasis (adjusted relative risk 0.58, 95% confidence interval 0.55-0.62).ConclusionAs well as hyperlipidemia, psoriasis significantly increased the risk of CKD. Statin treatment for hyperlipidemia reduced the risk of CKD in patients with psoriasis