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At least 289 records · Page 16
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NASA NTRS2017

Application of GPS to Enable Launch Vehicle Upper Stage Heliocentric Disposal

To properly dispose of the upper stage of the Space Launch System, the vehicle must perform a burn in Earth orbit to perform a close flyby of the Lunar surface to gain adequate energy to enter into heliocentric space. This architecture was selected to meet NASA requirements to limit orbital debris in the Earth-Moon system. The choice of a flyby for heliocentric disposal was driven by mission and vehicle constraints. This paper describes the SLS mission for Exploration Mission -1, a high level overview of the Block 1 vehicle, and the various disposal options considered. The research focuses on this analysis in terms of the mission design and navigation problem, focusing on the vehicle-level requirements that enable a successful mission. An inertial-only system is shown to be insufficient for heliocentric flyby due to large inertial integration errors from launch through disposal maneuver while on a trans-lunar trajectory. The various options for aiding the navigation system are presented and details are provided on the use of GPS to bound the state errors in orbit to improve the capability for stage disposal. The state estimation algorithm used is described as well as its capability in determination of the vehicle state at the start of the planned maneuver. This data, both dispersions on state and on errors, is then used to develop orbital targets to use for meeting the required Lunar flyby for entering onto a heliocentric trajectory. The effect of guidance and navigation errors on this capability is described as well as the identified constraints for achieving the disposal requirements. Additionally, discussion is provided on continued analysis and identification of system considerations that can drive the ability to integrate onto a vehicle intended for deep space.

Anzalone, Evan J.↗
NASA NTRS2005

Preparing for the Huygens Probe Mission, Cassini orbit determination results for the first and second targeted Titan encounters

Dynamic modeling of the spacecraft and Saturn system, tracking data, including radio-metric and optical navigation data, and measurement modeling associated with the final trajectory analysis are described. Navigation predictions produced during the operational phase are compared with the final trajectory in order to gain insight into navigation performance and maneuver execution errors. Special attention is given to refinement of the dynamical environment of Saturn, particularly Titan, during the first two orbits.

navigation↗
NASA NTRS1992

Compensating For GPS Ephemeris Error

Method of computing position of user station receiving signals from Global Positioning System (GPS) of navigational satellites compensates for most of GPS ephemeris error. Present method enables user station to reduce error in its computed position substantially. User station must have access to two or more reference stations at precisely known positions several hundred kilometers apart and must be in neighborhood of reference stations. Based on fact that when GPS data used to compute baseline between reference station and user station, vector error in computed baseline is proportional ephemeris error and length of baseline.

Wu, Jiun-Tsong↗
NASA NTRS1973

Study of effects of uncertainties on comet and asteroid encounter and contact guidance requirements. Part 1: Guidance and navigation studies

A guidance algorithm that provides precise rendezvous in the deterministic case while requiring only relative state information is developed. A navigation scheme employing only onboard relative measurements is built around a Kalman filter set in measurement coordinates. The overall guidance and navigation procedure is evaluated in the face of measurement errors by a detailed numerical simulation. Results indicate that onboard guidance and navigation for the terminal phase of rendezvous is possible with reasonable limits on measurement errors.

Source record↗
NASA NTRS1973

Solar electric propulsion for terminal flight to rendezvous with comets and asteroids

A guidance algorithm that provides precise rendezvous in the deterministic case while requiring only relative state information is developed. A navigation scheme employing only onboard relative measurements is built around a Kalman filter set in measurement coordinates. The overall guidance and navigation procedure is evaluated in the face of measurement errors by a detailed numerical simulation. Results indicate that onboard guidance and navigation for the terminal phase of rendezvous is possible with reasonable limits on measurement errors.

Bennett, A.↗
NASA NTRS1972

A detailed analysis of Mariner nine TV navigation data.

Mariner 9 data analysis showed a good performance of the Mars probe planetary approach navigation systems and a good agreement between measured and predicted probe-approach characteristics. It was found that all operations were completed on time and that the calibration of the instruments and the observation of a greater-than-planned number of stars resulted in a higher-than-expected measurement accuracy. The key instruments of the Mariner were TV cameras taking pictures of Phobos and Deimos against a background of stars, calibrated sun and star sensors, and a scan platform. The error models used for optical navigation system elements, the calibration of the scan platform and of the TV cameras, and the image detection and location techniques are discussed in detail.

Breckenridge, W. G.↗
NASA NTRS1992

A gravity field to support Magellan navigation and science at Venus

The development and validation of the revised JPL Venus Gravity Model are described with attention given to the incorporation of data regarding the longitudinal coverage. The motivation for the JPL Venus Gravity Model 1B (VGM1B) is related to the determination of orbit-support requirements for the Magellan mission. Existing gravity models for Venus are reviewed, and the present model is based on orbit-prediction data taken from Doppler tracking data from the Pioneer Venus Orbiter (PVO). Revised information arrays are developed incorporating more complete data describing the longitudinal conditions of the gravity field. Improvements are noted in the Doppler residual statistics taken from field-validation fits to the PVO and Magellan tracking data by using the VGM1B harmonic field. The VGM1B gravity field is also shown to reduce the trajectory errors from PVO and Magellan navigation.

Mcnamee, J. B.↗
NASA NTRS1973

Validity test for linear error analysis

To determine whether estimation process simulated by linear error analysis will converge, criterion has been developed based on extension of classical observability. Particular application of technique is with groups of batched navigation data where statistics of estimation errors are derived with classical minimum-variance methods.

Diamant, L. S.↗
NASA NTRS2017

Orbit Determination Covariance Analyses for the Parker Solar Probe Mission

This paper details pre-launch navigation covariance analyses for the Parker Solar Probe mission. Baseline models and error assumptions are outlined. The results demonstrate how navigation will satisfy requirements and are used to define operational plans. A few sensitivities are identified and the accompanying investigations are described. Predicted state uncertainty results show that most requirements are met with substantial margin. Moreover, navigation sensitivities may be accommodated operationally and this has been incorporated into project planning. Detailed results are presented only for select launch dates, however twenty unique trajectories (one per launch opportunity) have been assessed.

Jones, Drew Ryan↗
NASA NTRS1998

A Self-Tuning Kalman Filter for Autonomous Spacecraft Navigation

Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman Filter and Global Positioning System (GPS) data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. Current techniques of Kalman filtering, however, still rely on manual tuning from analysts, and cannot help in optimizing autonomy without compromising accuracy and performance. This paper presents an approach to produce a high accuracy autonomous navigation system fully integrated with the flight system. The resulting system performs real-time state estimation by using an Extended Kalman Filter (EKF) implemented with high-fidelity state dynamics model, as does the GPS Enhanced Orbit Determination Experiment (GEODE) system developed by the NASA Goddard Space Flight Center. Augmented to the EKF is a sophisticated neural-fuzzy system, which combines the explicit knowledge representation of fuzzy logic with the learning power of neural networks. The fuzzy-neural system performs most of the self-tuning capability and helps the navigation system recover from estimation errors. The core requirement is a method of state estimation that handles uncertainties robustly, capable of identifying estimation problems, flexible enough to make decisions and adjustments to recover from these problems, and compact enough to run on flight hardware. The resulting system can be extended to support geosynchronous spacecraft and high-eccentricity orbits. Mathematical methodology, systems and operations concepts, and implementation of a system prototype are presented in this paper. Results from the use of the prototype to evaluate optimal control algorithms implemented are discussed. Test data and major control issues (e.g., how to define specific roles for fuzzy logic to support the self-learning capability) are also discussed. In addition, architecture of a complete end-to-end candidate flight system that provides navigation with highly autonomous control using data from GPS is presented.

Truong, Son H.↗
NASA NTRS1992

Precision X-band radio Doppler and ranging navigation: Mars Observer interplanetary cruise scenario

This article describes an error covariance analysis based on a Mars Observer mission scenario; the study was performed to establish the navigation performance that can potentially be achieved in a demonstration of precision two-way X-band (8.4-GHz) Doppler and ranging with the Mars Observer spacecraft planned for next year, and to evaluate the sensitivity of the predicted performance to variations in ground system error modeling assumptions. Orbit determination error statistics computed for a 182-day Doppler and ranging data arc predicted Mars approach orbit determination accuracies of about 0.45 micro-rad in an angular sense, using a conservative ground system error model as a baseline. When less-conservative error model assumptions were employed, it was found that orbit determination accuracies of 0.19 to 0.30 micro-rad could be obtained; the level of accuracy of the assumed Mars ephemeris is about 0.11 micro-rad. In comparison, Doppler-only performance with the baseline error model was predicted to be about 1.30 to 1.51 micro-rad, although it was found that when improved station location accuracies and Global Positioning System-based tropospheric calibration accuracies were assumed, accuracies of 0.44 to 0.52 micro-rad were predicted. In the Doppler plus ranging cases, the results were relatively insensitive to variations in ranging system and station delay calibration uncertainties of a few meters and tropospheric zenith delay calibration uncertainties of a few centimeters.

Estefan, J. A.↗
NASA NTRS1976

Optical guidance vidicon test program

A laboratory and field test program was conducted to quantify the optical navigation parameters of the Mariner vidicons. A scene simulator and a camera were designed and built for vidicon tests under a wide variety of conditions. Laboratory tests characterized error sources important to the optical navigation process and field tests verified star sensitivity and characterized comet optical guidance parameters. The equipment, tests and data reduction techniques used are described. Key test results are listed. A substantial increase in the understanding of the use of selenium vidicons as detectors for spacecraft optical guidance was achieved, indicating a reduction in residual offset errors by a factor of two to four to the single pixel level.

Eiseman, A. R.↗
NASA NTRS1975

The background for Skylab experiment T-002, manual navigation sightings

The background of the NASA-DOD manual navigation experiment (T002) on Skylab A is reviewed with emphasis on NASA's development of an error model for sextant measurements in midcourse navigation and on USAF's development of a low earth orbit manual navigation scheme. Instruments briefly described are a space sextant and space stadimeter, both of which are used by USAF in orbit navigation, the sextant by NASA in midcourse sightings. The rationale, data requirements, and data reduction procedures are discussed in terms of the goals of the agencies.

Randle, R. J.↗
NASA NTRS1986

Phase noise from aircraft motion: Compensation and effect on synthetic aperture radar images

Image degradation of airborne SAR imagery caused by phase errors introduced in the received signal by aircraft motion is discussed. Mechanical motion has a small bandwidth and does not affect the range signal, where the total echo time is typically 60 microsec. However, since the aperture length can be several seconds, the synthesized azimuth signal can have significant errors of which phase noise is the most important. An inertial navigation system can be used to compensate for these errors when processing the images. Calculations to evaluate how much improvement results from compensation are outlined.

Gabriel, Andrew K.↗
NASA NTRS1984

The work on Comet Halley's orbit at ESOC

The predominant error source in the final navigation for the Giotto Comet fly-by of Halley's nucleus is due to uncertainties in the comet's ephemeris. Efforts are being undertaken at ESOC to improve the prediction of the comet's state at the time of the encounter. Some of the aspects involved in the problem discussed include ways to improve old observations by re-measurement or re-reduction and encouragement to observers to take fine quality astrometric observations in the future, especially at critical times. Difficulties in the mathematical modelling of the non-gravitational forces and possible offsets of the comet's center-of-light from its center-of-mass are addressed. The available estimation techniques are also examined including one based upon selecting optimum observations.

Morley, T.↗
NASA NTRS1992

Comparisons of the NASA ER-2 meteorological measurement system with radar tracking and radiosonde data

Measurements of aircraft longitude, latitude, and velocity, and measurements of atmospheric pressure, temperature, and horizontal wind from the meteorological measurement system (MMS) on board the NASA ER-2 aircraft were compared with independent measurements of these quantities from radiosondes and radar tracking of both the ER-2 and radiosonde balloons. In general, the comparisons were good and within the expected measurement accuracy and natural variability of the meteorological parameters. Radar tracking of the ER-2 resolved the velocity and position drift of the inertial navigation system (INS). The rms errors in the horizontal velocity components of the ER-2, due to INS errors, were found to be 0.5 m/s. The magnitude of the drift in longitude and latitude depends on the sign and magnitude of the corresponding component velocity drift and can be a few hundredths of a degree. The radar altitudes of the ER-2 and radiosondes were used as the basis for comparing measurements of atmospheric pressure, temperature, and horizontal wind from these two platforms. The uncertainty in the MMS horizontal wind measurement is estimated to be +/- 2.5 m/s. The accuracy of the MMS pressure and temperature measurements were inferred to be +/- 0.3 hPa and +/- 0.3 K.

Gaines, Steven E.↗
NASA NTRS1999

A Self-Tuning Kalman Filter for Autonomous Navigation Using the Global Positioning System (GPS)

Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman filter and GPS (Global Positioning Systems) data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. These systems, however, still rely on manual tuning from analysts. A sophisticated neuro-fuzzy component fully integrated with the flight navigation system can perform the self-tuning capability for the Kalman filter and help the navigation system recover from estimation errors in real time.

Truong, Son H.↗