Telemetry Data Rate Research Articles

Integrated design of ranging and DOR signal for China's deep space navigation

Abstract An integrated ranging and differential one-way range (DOR) signal design is implemented. The design utilizes the regenerative pseudo-noise ranging scheme and one pair of dedicated DOR tones for the deep space United X Band system. To demonstrate its effectiveness, it was applied to China’s Tianwen-1 orbiter and compared with the classic and normal designs. Using the link budget and error analysis methods, the measurement accuracy and communication ability were assessed. Results show that the novel design achieves better performance compared with that of the classic and normal designs. In the applied case, the power efficiency improved by > 30 % \gt 30 \% , two-way ranging precision improved from 0.50 to 0.09 m, and the two-way Doppler precision improved by 20% compared with those of the classic one. In addition, the spacecraft thermal noise during Delta-DOR measurements was slightly reduced. Owing to the higher downlink residual carrier, the supported telemetry data rate increased by 50%. Compared with the normal one, a higher downlink residual carrier (by 0.35 dB) was achieved by the novel design and resulted in slightly better ranging and Doppler accuracies. The novel design has a good technical foundation and is expected to be adopted in China’s future lunar and deep space explorations.

Analysis of the Advantages and Disadvantages of Astrometric and Geodetic VLBI Observation at Ka-band

The development and necessity of the frequency settings in astrometric and geodetic Very Long Baseline Interferometry (VLBI) observations are analyzed, especially on the advantages and disadvantages of observations at Ka-band. Compared to X-band, the advantages at Ka-band include more compact extragalactic sources, relatively smaller core shift effect, as well as efficiency to improve the precision in the realization of radio celestial reference frame and in the linkage to the quasi-inertia optical frame of Gaia project. Advantages in terms of deep space exploration are high in telemetry data rate, high in VLBI tracking precision, and helpful to mitigate the detrimental effects of ionosphere and solar plasma on the observed time delay. Disadvantages include relatively weak extragalactic sources, high precision requirement of reflector and antenna pointing, and susceptible to atmospheric absorption and emission effects. But the loss in system sensitivity due to these factors could be mostly compensated by the rapid development in high data rate sampling and recording technology. Finally in accordance with the current status of VLBI technique in China some specific recommendations for further development are recommended for criticism by readers.

Telemetry, telecommand and safety sub-systems for scientific ballooning from Hyderabad

Highly sophisticated balloon-borne scientific payloads have stringent requirement on the telemetry and command system. The development and fabrication of the on-board TT&C package for telemetry, tracking, command, safety and ranging for these experiments is done in-house at the National Balloon Facility (NBF) at Hyderabad. In the last few years, we have made major improvements both in the ground station and the on-board sub-systems, thereby improving the data quality, data handling speed and the general flight control along with aviation safety. The new system has telemetry data rate up to 1 Mbps. A reduction in weight, power and cost of the reengineered on-board integrated package has also lead to the ease of operation during field tests prior to launch and at remote recovery sites. In this paper, we describe the details of the new control package, its flight performance and our plans for portable S-band telemetry and telecommand system to cater to the balloon flights from Antarctic station and long duration balloon flights.

Integrated RF-optical TT&C for interplanetary telecomms

Science return and high bandwidth communications are one of the key issues to support the foreseen endeavours on next generation missions [J.L. Gerner, Telemetry, tracking and command of satellites—a perspective, TT&C 2004 Workshop, 7–9 September 2004]. Interplanetary telecommunication systems are required that support the foreseen endeavours. Given the same constraints in terms of mass, power and volume a laser communications terminal can offer an increase in telemetry bandwidth over classical RF technology allowing for a variety of new options, specifically to missions that require large distances, such as to the Moon, to liberation points L1 and L2, ultimately aiming at deep space missions. An increase in telemetry data rate allows the mission to consider the processing of raw scientific data to take place on ground, making use of latest technology further developed during the cruise phase of the probe, rather than applying data pre-processing on-board the satellite. Enhanced sensing techniques that generate more science data return could be used and access to data during flight could be faster. Results of on-going activities will be presented, comprising PPM laser communications and advanced tracking concepts. An overview will be given of the system concept for an integrated RF-optical TT&C transponder. Results will be shown from hardware tests on communications performance in inter-island test campaigns.

An Integrated Full-Wave CMOS Rectifier With Built-In Back Telemetry for RFID and Implantable Biomedical Applications

This paper describes the design and implementation of an integrated full-wave standard CMOS rectifier with built-in passive back telemetry mechanism for radio frequency identification (RFID) and implantable biomedical device applications. The new rectifier eliminates the need for additional large switches for load modulation and provides more flexibility in choosing the most appropriate load shift keying (LSK) mechanism through shorting and/or opening the transponder coil for any certain application. The results are a more robust back telemetry link, improved read range, higher back telemetry data rate, reduced rectifier dropout voltage, and saving in chip area compared to the traditional topologies. A prototype version of the new rectifier is implemented in the AMI 0.5- mum n-well 3-metal 2-poly 5 V standard CMOS process, occupying ~ 0.25 mm2 of chip area. The prototype rectifier was powered through a wireless inductive link and proved to be fully functional in its three modes of operation: rectification, open coil (OC), and short coil (SC).

The Demeter microsatellite and ground segment

The Demeter program is the first application of the Myriade microsatellite program conducted by the Cnes (French Space Agency) since 1997. The Myriade objective was to benefit from the miniaturization of the technologies to develop a product with a reduced size, weight and cost able to implement either scientific missions, demonstrators or operational applications in different areas: earth observation, astronomy, fundamental physics or telecommunications, within limited financial budget. The Demeter satellite was launched in end of June 2004, from Baikonour, aboard a Dnepr launcher, on a sun synchronous orbit at 710 km altitude. Its main scientific objectives are the detection and characterization of ionosphere electrical and magnetic disturbances in connection with a seismic activity. The scientific payload has been built by French scientific institutes (LPCE, CESR, CETP) involved in external and internal geophysics and by SSD/ESTEC (ESA). It is composed of several electrical and magnetic sensors, an ion spectrometer, an energetic particle analyzer and a Langmuir probe. The Demeter platform is designed in order to offer a high level of performances in terms of power, attitude and orbit control, data storage and transmission, flexibility. For example the large amount of scientific data is transmitted to the ground station with a high data rate telemetry link in X band. This paper describes the Demeter satellite and ground segment. It focuses on the specific design adaptations of the Myriade product for Demeter and it presents the preliminary in orbit platform performances.

Robots for lunar exploration: Present and future

Direct teleoperation of a rover on the moon has proven to be feasible but very demanding in telemetry data rate. Several modes are proposed to control the rover with lower communication data rates and the necessary equipments to operate the vehicle in these modes are identified. The impact of the equipment's mass and consumption on the minimal size of a rover is discussed for several applications.

A smart telemetry compression system for a space instrument: MARS-96 ELISMA instrument complex

A smart telemetry compression system has been developed for the ELISMA complex of instruments on MARS-96. Most of the data generated by the individual instruments of the complex require compression before transmission back to Earth since the complex is capable of producing data at many times the allocated ELISMA telemetry data rate. A compression algorithm was produced that could achieve a selectable compression ratio of 5:1, 6:1, or 7:1. An equivalent fuzzy logic controller sets the compression ratio for each data record of each individual instrument depending on: (i) the best ratio as determined by the variability of the data in that record; (ii) the instantaneous level of the data held in the telemetry buffer; and (iii) on the current usage of that instrument's data allocation for the present orbit around Mars.

Efficient modulation techniques for satellite telemetry—receiver design and performance evaluation

AbstractIn this paper we address the design of the data demodulator for high‐efficiency satellite communications suited for telemetry applications. We choose Gaussian minimum shift keying as the modulation format and analyse its relative merits with respect to the more traditional filtered offset quadrature phase‐shift keying scheme, when applied to medium‐to‐high data rate telemetry. Our study encompasses both geostationary orbits and the more challenging low earth orbit scenarios, and investigates the acquisition and tracking performance of the receiver with the aid of computer simulations. In particular, we present design criteria leading to the development of efficient, low‐complexity schemes for symbol timing and carrier phase/frequency recovery and we analyse the impact of these synchronization algorithms on the system performance. Next, we discuss the demodulator performance degradation when the transmitted signal is passed through on‐board solid‐state or travelling‐wave‐tube power amplifiers. The paper is concluded by a comparative analysis of the above modulation schemes, with special emphasis on their power and spectral efficiency.

Data aquisition and -evaluation electronics for the Rosat PSPCs

The German X-ray satellite Rosat will carry two redundant position sensitive proportional counters (PSPC) and a high resolution imager. For the PSPCs the corresponding front-end and evaluation electronics were designed and built at the MPI. For each accepted X-ray event in the energy range from 0.1 to 2.0 keV the energy and the arrival time as well as the location are determined. In order to reduce the telemetry data rate, the event location is calculated on board, using a microcomputer. A newly designed electronical background suppression system for charged particles was incorporated. By this system, a suppression efficiency of 97.5% was measured. Together with a five sided anticoincidence, 99% was achieved. Each of the PSPCs, of which only one at a time is active, contains its own charge sensitive amplifiers and pulse shapers. The analog signals of the PSPCs are mixed and routed to the commonly used analog evaluation electronics and the microcomputer. In order to reduce the number of peak detectors and analog to digital converters the signals are multiplexed. Up to 1000 events/s can be evaluated.

From 8-1/3 bits/s to 100,000 bits/s in ten years

During the first 11 years of its planetary program, the United States sent seven spacecraft to explore the inner planets: Venus, Mars, and Mercury. At the beginning of this period, the telemetry data rate was 8-1/3 bits/s; by the end of the period it was 120 kbits/s, a more than ten-thousand-fold increase. To identify the major factors involved, the form of a deep space telemetry system is described and the values of the major factors for each of the seven spacecraft are given. The amount of the improvement in each is computed and the way in which the improvement was achieved is discussed. Finally, some possible directions for possible future improvements are suggested.

Anomalous features of the electron density in the topside ionosphere

The instruments which measure electron density and temperature are quite separate and independent in operation, but on account of the limitations in power supply and telemetry data rate the two experiments share the same power lines and some data channels.

Data Considerations for Planetary Space Science Photography

Analog and digital data processes are discussed for interplanetary photoscience. Particular reference is made to the Mariner Mars flyby photo mission. A planetary flyby picture taking sequence produces a relatively fast accumulation of video data bits. This data is stored on magnetic tape. As the telemetry data rate at planetary range is extremely slow, days must elapse for continuous transmission of the stored picture information. A study of the analog and digital resolution criteria indicates that for the low contrast scenes viewed, a high SNR at the camera is desired. When the spacecraft is so limited in power, weight, and transmission capability, a ground based computer usefully enhances contrast and resolution.