Tracking and data acquisition system for the 1990's. Volume 8: TDAS frequency planning

Current planning calls for the TDAS to support new user and crosslink services, in addition to TDRSS-compatible services. TDRSS-compatible services would operate in current S-band and K-band channels used by TDRSS. New services, however, can take advantage of technology advances at microwave and optical frequencies. For augmented space-to-space services, 60 GHz and GaAs laser systems offer technical advantages, relative freedom from RFI, and a benign regulatory environment (i.e., minimal congestion and, in the case of 60 GHz, maximum regulatory support for TDAS-type services). For TDAS Earth-to-space and space-to-Earth services, the 30/20 GHz band offers the best mix of technical and regulatory advantages. But use of these bands would have to be coordinated with the U.S. military

Equilibrium properties of the Skylab CMG rotation law

The equilibrium properties of the control moment gyroscopes of the Skylab are discussed. A rotation law is developed to produce gimbal rates which distribute the angular momentum contributions among the control moment gyroscopes to avoid gimbal stop encounters. The implications for gimbal angle management under various angular momentum situations are described. Conditions were obtained for the existence of equilibria and corresponding stability properties

Improving Undergraduate Student Engagement in a Hybrid Research Course

Undergraduate nursing students have traditionally struggled to appreciate and understand research. Traditional teaching and learning methods in the research classroom are not meeting the needs of current students (McCurry & Martins, 2010), and innovations must be sought to overcome students\u27 resistance to research. Efforts to improve the early research utilization skills and attitudes of students is critical if we are to hope for the grounding of their future practice in evidence. To engage students in one hybrid research course, the faculty member created an innovative “March Madness” assignment that assists students in applying their learning. This article details how students engage in collaboration and friendly competition to implement critical research appraisal

Solar pointing variations in earth orbit and the impact on mission design

Solar pointing variations in earth orbit and impact on mission desig

The quasi-inertial and wide-deadband modes as backup attitude options for the Skylab mission

The quasi-inertial (QI) and wide deadband (WDB) modes were investigated as alternatives to the solar inertial (SI) mode in case two control moment gyros fail during the Skylab mission. Both modes provide a substantial reduction in propellant requirements from the solar interial hold requirement with either the orbital assembly/thruster attitude control system or service module reaction control system. Spacecraft motion in the QI mode is produced by a command rate and results in a small amplitude oscillation (17 deg, maximum) about the SI orientation. In the WDB mode a somewhat similar, but larger amplitude motion (35 deg maximum) about the SI orientation is developed by appropriate choice of controller deadbands and switch line slopes

Analysis of navigation performance for the Earth Observing System (EOS) using the TDRSS Onboard Navigation System (TONS)

Use of the Tracking and Data Relay Satellite System (TDRSS) Onboard Navigation System (TONS) was proposed as an alternative to the Global Positioning System (GPS) for supporting the Earth Observing System (EOS) mission. The results are presented of EOS navigation performance evaluation with respect to TONS based orbit, time, and frequency determination (OD/TD/FD). Two TONS modes are considered: one uses scheduled TDRSS forward link service to derive one way Doppler tracking data for OD/FD support (TONS-I); the other uses an unscheduled navigation beacon service (proposed for Advanced TDRSS) to obtain pseudorange and Doppler data for OD/TD/FD support (TONS-II). Key objectives of the analysis were to evaluate nominal performance and potential sensitivities, such as suboptimal tracking geometry, tracking contact scheduling, and modeling parameter selection. OD/TD/FD performance predictions are presented based on covariance and simulation analyses. EOS navigation scenarios and the contributions of principal error sources impacting performance are also described. The results indicate that a TONS mode can be configured to meet current and proposed EOS position accuracy requirements of 100 and 50 m, respectively

Tracking Data Acquisition System (TDAS) for the 1990's. Volume 6: TDAS navigation system architecture

One-way range and Doppler methods for providing user orbit and time determination are examined. Forward link beacon tracking, with on-board processing of independent navigation signals broadcast continuously by TDAS spacecraft; forward link scheduled tracking; with on-board processing of navigation data received during scheduled TDAS forward link service intervals; and return link scheduled tracking; with ground-based processing of user generated navigation data during scheduled TDAS return link service intervals are discussed. A system level definition and requirements assessment for each alternative, an evaluation of potential navigation performance and comparison with TDAS mission model requirements is included. TDAS satellite tracking is also addressed for two alternatives: BRTS and VLBI tracking

Teaching Information Literacy: A Review of 100 Syllabi

This study presents an analysis of 100 syllabi of creditbearing information literacy (IL) courses from colleges and universities across the United States. The objective was to determine how IL courses were being presented and taught in academic settings; how many credits were offered; the duration of the course; platform used to teach - face to face, online, or other methods; how students were graded; what types of assignments were used, and what topics were being taught and how. The authors hypothesized that over the course of six years since the original study, syllabi would show significant changes as technology has continued to dominate and expand the library world. Finally, the study looks to see how national IL courses address the Association of College and Research Libraries’ (ACRL) Information Literacy Competency Standards for Higher Education (the Standards). The importance of this research was to guide our own interest in developing a credit-bearing IL course as well as to provide this information for others in our profession who share an interest in this area

ISM In-Space Manufacturing

Develop and enable the technologies, materials, and processes required to provide affordable, sustainable on-demand manufacturing, recycling, and repair during Exploration Missions

Utilizing Multimedia Case Studies to Teach the Professional Side of Project Management

This research was conducted to evaluate the effectiveness of using a LITEE multimedia case study to teaching concepts in engineering courses. The LITEE Superstar case study was implemented in an engineering Project Management course. Numerous surveys regarding student expectations, outcomes, and attitudes were collected and results are presented herein. Overall, the study provided evidence that the students felt that the LITEE case study added value to the course via the different methods of teaching material, aided in the understanding of the project selection process, and ultimately helped them be successful in their course project which was conducted for a real rural Missouri city. The data was unable to be tracked on a per student basis; this yields areas for future research to track individual student improvement and attitudes. This research provides evidence that using multimedia case studies, such as the case studies published by LITEE, are effective and well received by engineering students in their coursework