SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 18 - SEPTEMBER 09, 2006

17 SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
Includes space systems telemetry; space communications networks; astronavigation and guidance; and spacecraft radio blackout.

For related information see also 04 Aircraft Communications and Navigation; and 32 Communications and Radar.

20050205016 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA, USA

7.3 Communications and Navigation

Manning, Rob; Capabilities Roadmap Briefings to the National Research Council; March 1, 2005; 18 pp.; In English; See also 20050205013; Original contains color illustrations; No Copyright; Avail: CASI; A03, Hardcopy; Available from CASI on CD-ROM only as part of the entire parent document

This presentation gives an overview of the networks NASA currently uses to support space communications and navigation, and the requirements for supporting future deep space missions, including manned lunar and Mars missions. The presentation addresses the Space Network, Deep Space Network, and Ground Network, why new support systems are needed, and the potential for catastrophic failure of aging antennas. Space communications and navigation are considered during Aerocapture, Entry, Descent and Landing (AEDL) only in order to precisely position, track and interact with the spacecraft at its destination (moon, Mars and Earth return) arrival. The presentation recommends a combined optical/radio frequency strategy for deep space communications. Derived from text

Space Communication; Space Navigation; Ground Support Systems; Ground Stations; Antennas; Deep Space; Manned Mars Missions

20050205863 NASA Glenn Research Center, Cleveland, OH, USA, Ohio Board of Regents, OH, USA, Ohio Univ., OH, USA

ACTS Operations Extended Through a University-Based Consortium

Bauer, Robert A.; Krawczyk, Richard J.; Research and Technology 2001; March 2002; 3 pp.; In English; No Copyright;Avail: CASI; A01, Hardcopy

The Advanced Communications Technology Satellite (ACTS) program was slated for decommissioning in October 2000. With plans in place to move the spacecraft to an orbital graveyard and then shut the system down, NASA was challenged to consider the feasibility of extending operations for education and research purposes provided that an academic organization would be willing to cover operations costs. This was determined to be viable, and in the fall of 2000, NASA announced that it would consider extending operations. On March 19, 2001, NASA, the Ohio Board of Regents, and the Ohio University signed a Space Act Agreement to continue ACTS operations for 2 more years with options to extend operations up to a total of 4 years. To accomplish this, the Ohio University has formed a university-based consortium, the Ohio Consortium for Advanced Communications Technology (OCACT), and acts as the managing member. The Ohio University is responsible for the full reimbursement of NASA’s operations costs, and does this through consortium membership. NASA retains the operating license of the spacecraft and has two contractors supporting spacecraft and master control station operations. This flexible arrangement between NASA and academia allows the education community to access a large communications satellite for learning about spacecraft operations and to use the system’s transponders for communications applications. It also allows other organizations, such as commercial companies, to become consortium members and use the ACTS wideband Ka-band (30/20 GHz) payload. From the consortium members, six areas of interest have been identified. Derived from text

ACTS; University Program; Satellite Communication

20050205867 NASA Glenn Research Center, Cleveland, OH, USA, Science Applications International Corp., USA

Architecture Studies Done for High-Rate Duplex Direct Data Distribution (D4) Services

Research and Technology 2001; March 2002; 3 pp.; In English; No Copyright; Avail: CASI; A01, Hardcopy

A study was sponsored to investigate a set of end-to-end system concepts for implementing a high-rate duplex direct data distribution (D4) space-to-ground communications link. The NASA Glenn Research Center is investigating these systems (both commercial and Government) as a possible method of providing a D4 communications service between NASA spacecraft in low Earth orbit and the respective principal investigators using or monitoring instruments aboard these spacecraft. Candidate commercial services were assessed regarding their near-term potential to provide a D4 type of service. The candidates included K-band and V-band geostationary orbit and nongeostationary orbit satellite relay services and direct downlink (D3) services. Internet protocol (IP) networking technologies were evaluated to enable the user-directed distribution and delivery of science data. Four realistic, near-future concepts were analyzed: 1) A duplex direct link (uplink plus downlink communication paths) between a low-Earth-orbit spacecraft and a principal-investigator-based autonomous Earth station; 2) A space-based relay using a future K-band nongeosynchronous-orbit system to handle both the uplink and downlink communication paths; 3) A hybrid link using both direct and relay services to achieve full duplex capability; 4) A dual-mode concept consisting of both a duplex direct link and a space relay duplex link operating independently. The concepts were analyzed in terms of contact time between the NASA spacecraft and the communications service and the achievable data throughput. Throughput estimates for the D4 systems were based on the infusion of advanced communications technology products (single and multibeam K-band phased-arrays and digital modems) being developed by Glenn. Cost estimates were also performed using extrapolated information from both terrestrial and current satellite communications providers. The throughput and cost estimates were used to compare the concepts. Derived from text

Data Links; End-to-End Data Systems; Satellite Communication

20050205888 Observatoire de la Cote d’Azur, Grasse, France

Celestial Reference Systems - An Overview

Kovalevsky, J.; Mar. 2000; 8 pp.; In English Report No.(s): AD-A435384; No Copyright; Avail: Defense Technical Information Center (DTIC)

The paper starts with a short presentation of the conceptual foundations of celestial reference systems and of the IAU decisions taken in 1991.

The necessity to define and use them in the framework of General Relativity induces some difficulties that are analyzed.

In the case of kinematically defined reference systems, the origins of a possible residual rotation of the frames is analyzed.

The same analysis holds also for an isolated dynamical reference system, for which further developments of the metric are necessary.

Finally, a few topics concerning the non-isolated case of the barycentric reference system, the transformation between reference systems, and the significance of measurements are mentioned. DTIC

Celestial Navigation; Celestial Reference Systems; Relativity

20050206355 NASA Marshall Space Flight Center, Huntsville, AL, USA

Comparison of Two IRI Plasmasphere Extensions with GPS-TEC Observations

Gulyacva, Tamara; Gallagher, Dennis; [2005]; 1 pp.; In English; IRI 2005 Workshop, 27 Jun. - 1 Jul. 2005, Roquetes, Spain; No Copyright; Avail: Other Sources; Abstract Only

Two plasmasphere extensions of the International Reference Ionosphere are made available for the users. It is aimed to estimate the effect of charged particles on technical devices in the Earth’s environment and to define the ionosphereplasmasphere operational conditions compatible with existing and future systems of radio communication, radio navigation and other relevant radio technologies in the ranges of medium and higher frequencies. The Global Core Plasma Model (GCPM-2000) of Gallagher et al. (2000) is an empirical description of thermal plasma densities in the plasmasphere, plasmapause, magnetospheric trough, and polar cap. GCPM-2000 uses the Kp index and is coupled to IRI in the transition region 500-600 km. The IZMIRAN plasmasphere model (Chasovitin et al., 1998; Gulyaeva et al., 2002) is an empirical model based on whistler and satellite observations. It presents global vertical analytical profiles of electron density smoothly fitted to IRI electron density profile at 1000 km altitude and extended towards the plasmapause (up to 36,000 km). For the smooth fitting of the two models, the shape of the IRI topside electron density profile is improved using ISIS 1, ISIS 2, and IK19 satellite inputs (Gulyaeva, 2003). The plasmasphere model depends on solar activity and magnetic activity (kp-index). The two IRI plasmasphere extensions are compared in the present study with the total electron content derived from records of Global Positioning Satellites (GPS-TEC) observations for different latitudinal, solar activity, magnetic activity, diurnal and seasonal conditions. The differences of model TEC with observed TEC in the topside ionosphere and plasmasphere are discussed. Author

Radio Communication; Radio Navigation; Plasmasphere; Earth Ionosphere; Electron Density (Concentration); Electron Density Profiles; Charged Particles; Plasma Density

20050207441 NASA Dryden Flight Research Center, Edwards, CA, USA

Space-Based Range Safety and Future Space Range Applications

Whiteman, Donald E.; Valencia, Lisa M.; Simpson, James C.; August 2005; 14 pp.; In English Report No.(s): NASA/TM-2005-213662; H-2616; No Copyright; Avail: CASI; A03, Hardcopy

The National Aeronautics and Space Administration Space-Based Telemetry and Range Safety study is a multiphase project to demonstrate the performance, flexibility and cost savings that can be realized by using space-based assets for the Range Safety (global positioning system metric tracking data, flight termination command and range safety data relay) and Range User (telemetry) functions during vehicle launches and landings. Phase 1 included flight testing S-band Range Safety and Range User hardware in 2003 onboard a high-dynamic aircraft platform at Dryden Flight Research Center (Edwards, California) using the NASA Tracking and Data Relay Satellite System as the communications link. The current effort, Phase 2, includes hardware and packaging upgrades to the S-band Range Safety system and development of a high data rate Ku-band Range User system. The enhanced Phase 2 Range Safety Unit provided real-time video for three days during the historic GlobalFlyer (Scaled Composites, Mojave, California) flight in March, 2005. Additional Phase 2 testing will include a sounding rocket test of the Range Safety system and aircraft flight testing of both systems. Future testing will include a flight test on a launch vehicle platform. This report discusses both Range Safety and Range User developments and testing with emphasis on the Range Safety system. The operational concept of a future space-based range is also discussed. Author

Range Safety; Telemetry; Global Positioning System; Communication Networks; Real Time Operation

Source: NASA.