International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Wireless interfaces are becoming ubiquitous in terrestrial applications ranging from local area networking in business and commercial environments to large scale factory automation and process control. The pressure to develop these wireless interfacing techniques has come from the need to reduce cabling, reduce installation costs, and make it easier to extend network infrastructures. Concerns about electromagnetic compatibility, safety, reliability, and security have lead to the development of techniques and protocols that enable such wireless interfaces to be operated in electromagnetically harsh environments, without generating unacceptable interference, and providing reliable, dependable and secure data communications. On the face of it, the use of wireless interfaces onboard spacecraft looks like a good way of reducing the spacecraft harness mass and bulk. However, recent work by the European Space Agency has shown that, while harness reduction will undoubtedly be one benefit of using wireless interfaces, they offer many other benefits that will be more significant in the near future. Amongst these are significant advantages during integration and testing, the ability to retrofit and upgrade facilities, and cable replacement in moving structures such as robotic arms. In this paper we briefly survey the benefits of wireless interface technologies for spacecraft onboard use, and identify the challenges involved in adapting them for flight use. We then look at the considerations that should be taken into account in establishing the financial case for developing wireless interface technologies for flight applications.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A data driven telemetry system is described that responds to the rapid nature in which experimental satellite telemetry content is changed during the development process. It also meets the needs of a diverse experiment in which the many phases of a mission may contain radically different types of telemetry data. The system emphasizes mechanisms for achieving high redundancy of critical data. A practical example of such an implementation, Brilliant Pebbles Flight Experiment Three (FE-3), is cited.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Stanford’s Space Systems Development Laboratory is developing methods for automated spacecraft health operations. Such operations greatly reduce the need for ground-space communication links and full-time operators. However, new questions emerge about how to supply operators with the spacecraft information that is no longer available. One solution is to introduce a low-bandwidth health beacon and to develop new approaches in on-board summarization of health data for telemetering. This paper reviews the development of beacon operations and data summary, describes the implementation of beacon-based health management on board SAPPHIRE, and explains the mission operations response to health emergencies. Additional information is provided on the role of SSDL’s academic partners in developing a worldwide network of beacon receiving stations.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / Over the last several years, the Data Systems Technology Division (DSTD) at Goddard Space Flight Center (GSFC) has developed software tools to generate simulated spacecraft data to support the development, test, and verification of prototype and production of its Very Large Scale Integration (VLSI) telemetry data systems. Recently, these data simulation tools have demonstrated their versatility and flexibility in the testing and deployment of several very high performance Level Zero Processing (LZP) systems. Because LZP involves the wide scale reordering of transmitted telemetry data, the data simulation tools were required to create a number of very large and complex simulated data sets to effectively test these high rate systems. These data sets simulated spacecraft with numerous instrument data sources downlinking out-of-sequence and errored data streams. Simulated data streams were encapsulated in Consultative Committee for Space Data Systems (CCSDS) packet and NASCOM data formats. The knowledge and expertise gained in the development of the current simulation tools has been used to develop a new generation data simulation tool, known as the Simulated Telemetry Generation (STGEN) package. STGEN is a menu driven software package running on UNIX platforms that can implement dynamic test scenarios with very fast turn around times from the data set design to the data set generation. The error options and locations in the telemetry data stream are fed via simple programs which are in turn script-driven. Scripts are used to manipulate packets, frames, and permit error insertion more easily and quickly. This paper first describes the STGEN software package and its test data design strategies. It then provides an example of STGEN 's first usage in the testing of systems to support EOS-AM spacecraft. Finally, a description of future planned improvements and uses of STGEN are provided.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / As Mobile Satellite Communication Systems (MSCS), such as INMARSAT, Iridium, Globalstar, ICO, et al, are emerging, the feasibility analysis of MSCS using for spacecraft TT&C data transmission have been studied by many space agencies and scientists. In this paper, the usability of MSCS’s low data transmission for modern spacecraft is analyzed. The availability of existing and near future MSCS are reviewed briefly in terms of orbital coverage, data transmission rate, EIRP, adaptability and so on. The special problems to be resolved are discussed such as compensation for high Doppler frequency shift, provision of user spacecraft EIRP, antenna beams steering of user spacecraft, use of advanced modulation scheme.

The decentralized consensus control of a formation of rigid-body spacecraft is studied in the framework of geometric mechanics while accounting for a constant communication time delay between spacecraft. The relative position and attitude (relative pose) are represented on the Lie group SE(3) and the communication topology is modeled as a digraph. The consensus problem is converted into a local stabilization problem of the error dynamics associated with the Lie algebra se(3) in the form of linear time-invariant delay differential equations with a single discrete delay in the case of a circular orbit, whereas it is in the form of linear time-periodic delay differential equations in the case of an elliptic orbit, in which the stability may be assessed using infinite-dimensional Floquet theory. The proposed technique is applied to the consensus control of four spacecraft in the vicinity of a Molniya orbit.

Small satellites are becoming increasingly appealing as technology advances and shrinks in both size and cost. The development time for a small satellite is also much less compared to a large satellite. For small satellites to be successful, the navigation systems must be accurate and very often they must be autonomous. For lunar navigation, contact with a ground station is not always available and the system needs to be robust. The extended Kalman filter is a nonlinear estimator that has been used on-board spacecraft for decades. The filter requires linear approximations of the state and measurement models. In the past few years, the unscented Kalman filter has become popular and has been shown to reduce estimation errors. Additionally, the Jacobian matrices do not need to be derived in the unscented Kalman filter implementation. The intent of this research is to explore the capabilities of the extended Kalman filter and the unscented Kalman filter for use as a navigation algorithm on small satellites. The filters are applied to a satellite orbiting the Moon equipped with an inertial measurement unit, a sun sensor, a star camera, and a GPS-like sensor. The position, velocity, and attitude of the spacecraft are estimated along with sensor biases for the IMU accelerometer, IMU gyroscope, sun sensor and star camera. The estimation errors are compared for the extended Kalman filter and the unscented Kalman filter for the position, velocity and attitude. The analysis confirms that both navigation algorithms provided accurate position, velocity and attitude. The IMU gyroscope bias was observable for both filters while only the IMU accelerometer bias was observable with the extended Kalman filter. The sun sensor biases and the star camera biases were unobservable. In general, the unscented Kalman filter performed better than the extended Kalman filter in providing position, velocity, and attitude estimates but requires more computation time. / text

Project Upsilon is a proposed NASA Flagship Class, Uranus Orbiter and Probe mission concept to investigate Uranus' planetary magnetic field and atmosphere. Three spacecraft - the Upsilon-0 Propulsion Module, the Upsilon-1 Science Orbiter, and the Upsilon-2 Atmosphere Probe - shall be implemented to meet needs, goals, and objectives as stated by the NASA Solar System Planetary Science Decadal Survey 2013-2022. Upsilon-0 shall be expended in order to complete orbital capture about Uranus. Upsilon-1 shall study Uranus' planetary magnetic field, obtaining real-time measurements for nominally 20 months within the first two years of arrival; and for as long as possible after the first two years, as part of an extended science mission. Upsilon-2 shall be descended into Uranus' cloud tops to obtain physical data and imagery well into the atmosphere's depths. Chemical propulsion is employed in place of solar-electric propulsion, with regard to the interplanetary system-level trade tree. The interplanetary trajectory requires a single un-powered flyby of Jupiter, selected among several flyby node configurations. The science orbit produces nearly repeating latitude-longitude tracks over a rotating Uranus. The statistical estimation method combines an orbit determination model with respect to Uranus' flattening, and a simple magnetic dipole model for field line modeling. A 7-year period is allotted for the technology research and development, and the testing and verification stages of the project life cycle; the interplanetary journey to Uranus requires 21 years; and the nominal in-situ operation lifetime is 2 years. The Project Upsilon spacecraft launch in 2021 to "revolutionize our understanding of ice giant properties and processes, yielding significant insight into their evolutionary history"; contributing to the Planetary Science Decadal Survey's, and NASA's, key planetary science and deep space exploration visions. / text

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / With the development of microcomputer technology, the application of strap-down inertial navigation on aircraft is used more frequently. The attitude measurement for miniature spacecraft is most important. Installing three-axis acceleration sensors and three-axis rate gyros on the spacecraft, the accelerations and attitudes can be obtained through the PCM/FM telemetry system. Then, the initial attitude of spacecraft is given through outside measurement and telemetry. Finally, in the ground station, the parameters of spacecraft attitude are given by using strapdown inertial navigation theory and quanternion differential equation for solving the attitude.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Recommendations of the Consultative Committee for Space Data Systems (CCSDS) provide a standard approach for implementing spacecraft packet telemetry and command interfaces. The Fast Auroral Snapshot (FAST) Small Explorer mission relies heavily on the CCSDS virtual channel and packetization concepts to achieve near real-time commanding and distribution of telemetry between separate space borne science and spacecraft processors and multiple ground stations. Use of the CCSDS recommendations allows the FAST mission to realize significant re-use of ground systems developed for the first Small Explorer mission, and also simplifies system interfaces and interactions between flight software developers, spacecraft integrators, and ground system operators.