A study of planetary-approach orbit- determination policies using Mariner IV DOPPLER data
Planetary approach orbit determination target errors using Mariner IV Doppler tracking data
DOPPLER RADAR↗
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Orbit determination by range-only data.
The determination of satellite orbits for use in geodesy using range-only data has been examined. A recently developed recursive algorithm for rectification of the nominal orbit after processing each observation has been tested. It is shown that when a synchronous satellite is tracked simultaneously with a subsynchronous geodetic target satellite, the orbits of each may be readily determined by processing the range information. Random data errors and satellite perturbations are included in the examples presented.
Duong, N.↗
The Mariner Jupiter/Uranus 1979 mission
Some results of recent planning studies for a Mariner Jupiter/Uranus 1979 (MJU 79) mission are discussed. It is noted that a 1979 launch will provide unique approach geometries to Uranus because, when viewed from an approaching spacecraft in 1985, the pole-on orientation of the planet and its satellite orbit tracks will seem to describe a target, permitting a long observational period of almost all the lighted hemispheres of Uranus and its five known satellites. The overall scientific objectives for a MJU 79 mission are outlined, and mission considerations are discussed, including energy requirements, use of a Jupiter gravity-assist to reduce flight-time and launch vehicle-capability requirements, and various dual-launch strategies. Basic trajectories for Jupiter and Uranus encounters are considered, and general characteristics of the MJU 79 spacecraft are described. Expected scientific returns from a typical Uranus encounter is examined, including high-resolution scanning of the planet and its satellites, more accurate estimates of satellite radii and masses, and high-resolution IR studies of the planet.
Hyde, J. R.↗
Shoe-box orbit determination system for SMM preliminary results
The implementation of both sequential and batch methods of estimation on IMP-16 microprocessors was investigated. Simulated data was used from a tracking and data relay satellite whose target satellite was the Solar Maximum Mission. An interesting feature of the hardware was the use of two interconnected IMP-16's. Some preliminary results from the study, as well as the difficulties and advantages in the use of microprocessors, are presented.
Tasaki, K. K.↗
Shuttle orbiter radar cross-sectional analysis
Theoretical and model simulation studies on signal to noise levels and shuttle radar cross section are described. Pre-mission system calibrations, system configuration, and postmission system calibration of the tracking radars are described. Conversion of target range, azimuth, and elevation into radar centered east north vertical position coordinates are evaluated. The location of the impinging rf energy with respect to the target vehicles body axis triad is calculated. Cross section correlation between the two radars is presented.
Cooper, D. W.↗
Quaternions for Galileo scan platform control
The application of quaternions for the articulation control of the Galileo scan platform is presented in this paper. The purpose of selecting quaternions is to minimize onboard computation time and program size. Attention has been focused on performing inertial pointing while the spacecraft is in a dual spin configuration. Target quaternion and relative target quaternion are introduced and used to specify the target position of the scan platform for point-to-point absolute slews and mosaic relative slews, respectively. The pointing error of the platform is represented by an error quaternion which is converted into gimbal angular errors defining the attitude change. For path control, a moving target quaternion is generated; the corresponding tracking error quaternion and the related spacecraft motion compensation capability are also addressed. A sample slew case is used to demonstrate the implementation of these concepts.
Breckenridge, W. G.↗
Shuttle communication and tracking systems signal design and interface compatibility analysis
Various options for the Dedicated Payload Communication Link (DPCL) were evaluated. Specific subjects addressed include: payload to DPCL power transfer in the proximity of the payload, DPCL antenna pointing considerations, and DPCL transceiver implementations which can be mounted on the deployed antenna boom. Additional analysis of the Space Telescope performance was conducted. The feasibility of using the Global Positioning System (GPS) for attitude determination and control for large spacecraft was examined. The objective of the Shuttle Orbiter Radar Test and Evaluation (SORTE) program was to quantify the Ku-band radar tracking accuracy using White Sands Missile Range (WSMR) radar and optical tracking equipment, with helicopter and balloon targets.
Source record↗
Modeling and sensory feedback control for space manipulators
The positioning control problem of the endtip of space manipulators whose base are uncontrolled is examined. In such a case, the conventional control method for industrial robots based on a local feedback at each joint is not applicable, because a solution of the joint displacements that satisfies a given position and orientation of the endtip is not decided uniquely. A sensory feedback control scheme for space manipulators based on an artificial potential defined in a task-oriented coordinates is proposed. Using this scheme, the controller can easily determine the input torque of each joint from the data of an external sensor such as a visual device. Since the external sensor is mounted on the unfixed base, the manipulator must track the moving image of the target in sensor coordinates. Moreover the dynamics of the base and the manipulator are interactive. However, the endtip is proven to asymptotically approach the stationary target in an inertial coordinate frame by the Liapunov's method. Finally results of computer simulation for a 6-link space manipulator model show the effectiveness of the proposed scheme.
Masutani, Yasuhiro↗
Experimental validation of docking and capture using space robotics testbeds
This presentation describes the application of robotic and computer vision systems to validate docking and capture operations for space cargo transfer vehicles. Three applications are discussed: (1) air bearing systems in two dimensions that yield high quality free-flying, flexible, and contact dynamics; (2) validation of docking mechanisms with misalignment and target dynamics; and (3) computer vision technology for target location and real-time tracking. All the testbeds are supported by a network of engineering workstations for dynamic and controls analyses. Dynamic simulation of multibody rigid and elastic systems are performed with the TREETOPS code. MATRIXx/System-Build and PRO-MATLAB/Simulab are the tools for control design and analysis using classical and modern techniques such as H-infinity and LQG/LTR. SANDY is a general design tool to optimize numerically a multivariable robust compensator with a user-defined structure. Mathematica and Macsyma are used to derive symbolically dynamic and kinematic equations.
Spofford, John↗
Topographic slope from the SAR interferometric phase gradient
A new algorithm for the direct calculation of topographic slope maps from synthetic aperture radar (SAR) interferograms is presented. The algorithm derives slope maps without first requiring the creation of a digital elevational model (DEM) from the interferogram, thus obviating the need for high SNR in the interferogram and altitude calibration points for the scene. SAR data useful for interferometry has been collected by the Active Microwave Imager on board the ERS-1 satellite, when it was in a short period repeat orbit. Two passes of the radar sensor form a cross-track interferometric baseline. For a point target at some position (x,y,h), the interferometric phase difference phi is proportional to the difference in path lengths for the two sensor positions to the scatterer. Given the phase difference as measured in the complex interferogram and an accurate baseline geometry, the position of the scatterer, most significantly the height h, can be determined through triangulation. The interferometric phase measurement however is known only modulo 2-pi, and hence it is necessary to determine the correct multiple of 2-pi to add to the phase at each point to obtain an estimate of the actual phase with respect to an absolute datum. This phase unwrapping process is required for creating DEM's, and is difficult or impossible for regions of low SNR or SAR image layover. The new algorithm described here derives slope maps without requiring phase unwrapping.
Werner, Charles L.↗
The AEDC aerospace chamber 7V: An advanced test capability for infrared surveillance and seeker sensors
An advanced sensor test capability is now operational at the Air Force Arnold Engineering Development Center (AEDC) for calibration and performance characterization of infrared sensors. This facility, known as the 7V, is part of a broad range of test capabilities under development at AEDC to provide complete ground test support to the sensor community for large-aperture surveillance sensors and kinetic kill interceptors. The 7V is a state-of-the-art cryo/vacuum facility providing calibration and mission simulation against space backgrounds. Key features of the facility include high-fidelity scene simulation with precision track accuracy and in-situ target monitoring, diffraction limited optical system, NIST traceable broadband and spectral radiometric calibration, outstanding jitter control, environmental systems for 20 K, high-vacuum, low-background simulation, and an advanced data acquisition system.
Simpson, W. R.↗
Adaptation of the phase of the human linear vestibulo-ocular reflex (LVOR) and effects on the oculomotor neural integrator
The phase of the translational linear VOR (LVOR) can be adaptively modified by exposure to a visual-vestibular mismatch. We extend here our earlier work on LVOR phase adaptation, and discuss the role of the oculomotor neural integrator. Ten subjects were oscillated laterally at 0.5 Hz, 0.3 g peak acceleration, while sitting upright on a linear sled. LVOR was assessed before and after adaptation with subjects tracking the remembered location of a target at 1 m in the dark. Phase and gain were measured by fitting sine waves to the desaccaded eye movements, and comparing sled and eye position. To adapt LVOR phase, the subject viewed a computer-generated stereoscopic visual display, at a virtual distance of 1 m, that moved so as to require either a phase lead or a phase lag of 53 deg. Adaptation lasted 20 min, during which subjects were oscillated at 0.5 Hz/0.3 g. Four of five subjects produced an adaptive change in the lag condition (range 4-45 deg), and each of five produced a change in the lead condition (range 19-56 deg), as requested. Changes in drift on eccentric gaze suggest that the oculomotor velocity-to-position integrator may be involved in the phase changes.
Non-NASA Center↗
Covid-19 Impact Monitoring for Climate Environment (Greenhouse Gases)
To track atmospheric CO2 changes resulting from the lockdowns, observations collected by the NASA Orbiting Carbon Observatory-2 (OCO-2) satellite and Japan’s Greenhouse gases Observing SATellite (GOSAT) in 2020 were compared to results collected in previous years. The OCO-2 results were used to search for changes on regional scales over the globe. Targeted observations from GOSAT were used to track changes in large urban areas, such as Beijing and Tokyo. Both types of observations yielded key insights into the CO2 changes accompanying the economic disruptions caused by the COVID-19 lockdowns. ESA, NASA and JAXA developed the dashboard jointly to monitor the climate impacts of COVID-19.
greenhouse gases↗
Orion Ground Test Article Water Impact Tests: Photogrammetric Evaluation of Impact Conditions
The Ground Test Article (GTA) is an early production version of the Orion Crew Module (CM). The structural design of the Orion CM is being developed based on LS-DYNA water landing simulations. As part of the process of confirming the accuracy of LS-DYNA water landing simulations, the GTA water impact test series was conducted at NASA Langley Research Center (LaRC) to gather data for comparison with simulations. The simulation of the GTA water impact tests requires the accurate determination of the impact conditions. To accomplish this, the GTA was outfitted with an array of photogrammetry targets. The photogrammetry system utilizes images from two cameras with a specialized tracking software to determine time histories for the 3-D coordinates of each target. The impact conditions can then be determined from the target location data.
Vassilakos, Gregory J.↗
Multi-agent autonomous system
A multi-agent autonomous system for exploration of hazardous or inaccessible locations. The multi-agent autonomous system includes simple surface-based agents or craft controlled by an airborne tracking and command system. The airborne tracking and command system includes an instrument suite used to image an operational area and any craft deployed within the operational area. The image data is used to identify the craft, targets for exploration, and obstacles in the operational area. The tracking and command system determines paths for the surface-based craft using the identified targets and obstacles and commands the craft using simple movement commands to move through the operational area to the targets while avoiding the obstacles. Each craft includes its own instrument suite to collect information about the operational area that is transmitted back to the tracking and command system. The tracking and command system may be further coupled to a satellite system to provide additional image information about the operational area and provide operational and location commands to the tracking and command system.
Fink, Wolfgang↗
Digital accumulators in phase and frequency tracking loops
Results on the effects of digital accumulators in phase and frequency tracking loops are presented. Digital accumulators or summers are used extensively in digital signal processing to perform averaging or to reduce processing rates to acceptable levels. For tracking the Doppler of high-dynamic targets at low carrier-to-noise ratios, it is shown through simulation and experiment that digital accumulators can contribute an additional loss in operating threshold. This loss was not considered in any previous study and needs to be accounted for in performance prediction analysis. Simulation and measurement results are used to characterize the loss due to the digital summers for three different tracking loops: a digital phase-locked loop, a cross-product automatic frequency tracking loop, and an extended Kalman filter. The tracking algorithms are compared with respect to their frequency error performance and their ability to maintain lock during severe maneuvers at various carrier-to-noise ratios. It is shown that failure to account for the effect of accumulators can result in an inaccurate performance prediction, the extent of which depends highly on the algorithm used.
Hinedi, Sami↗
Near Earth Asteroid Scout - Mission Update
After its deployment from NASA’s Space Launch System (SLS), the Near-Earth Asteroid (NEA) Scout mission will travel to and image an asteroid during a close flyby using an 86m^2 solar sail as its primary propulsion. Solar sails are large, mirror-like structures made of a lightweight material that reflects sunlight to propel the spacecraft. The continuous solar photon pressure provides thrust with no need for the heavy, expendable propellants used by conventional chemical and electric propulsion systems. Developed by NASA’s Marshall Space Flight Center (MSFC) and Jet Propulsion Laboratory (JPL), the NEA Scout is based on the industry-standard CubeSat form factor. The spacecraft measures 11 cm x 24 cm x 36 cm and weighs less than 14 kilograms. Following deployment from the Space Launch System (SLS), the solar sail will deploy, and the spacecraft will begin its 2.0 – 2.5-year journey. About one month before the asteroid flyby, NEA Scout will search for the target and start its Approach Phase using a combination of radio tracking and optical navigation and perform a relatively slow flyby (10-20 m/s) of the target. A summary of the mission, sailcraft, mission design, and its first several months of deep space operation will be described.
Near Earth Asteroid↗
Multi-sensor Testing for Automated Rendezvous and Docking
During the past two years, many sensors have been tested in an open-loop fashion in the Marshall Space Flight Center (MSFC) Flight Robotics Laboratory (FRL) to both determine their suitability for use in Automated Rendezvous and Docking (AR&D) systems and to ensure the test facility is prepared for future multi-sensor testing. The primary focus of this work was in support of the CEV AR&D system, because the AR&D sensor technology area was identified as one of the top risks in the program. In 2006, four different sensors were tested individually or in a pair in the MSFC FRL. In 2007, four sensors, two each of two different types, were tested simultaneously. In each set of tests, the target was moved through a series of pre-planned trajectories while the sensor tracked it. In addition, a laser tracker "truth" sensor also measured the target motion. The tests demonstrated the functionality of testing four sensors simultaneously as well as the capabilities (both good and bad) of all of the different sensors tested. This paper outlines the test setup and conditions, briefly describes the facility, summarizes the earlier results of the individual sensor tests, and describes in some detail the results of the four-sensor testing. Post-test analysis includes data fusion by minimum variance estimation and sequential Kalman filtering. This Sensor Technology Project work was funded by NASA's Exploration Technology Development Program.
Howard, Richard T.↗