SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The Mars Pathfinder mission, scheduled for launch in December, 1996, will use an airbag system to safely deliver a lander to the Martian surface. The airbag landing system has undergone a comprehensive test program during its evolution from initial design phase to final qualification and acceptance testing.
Measurements of Mars' rotational variations can be conducted via Earth-based radio tracking observations of the Mars Pathfinder lander during an extended mission. Two-way range measurements between an Earth antenna and the lander will enable precise monitoring of the planet's orientation and length-of-day variation, allowing details of Mars' internal structure and global surface/atmosphere interactions to be determined with precision for the first time.
The Mars Pathfinder Project is being developed to demonstrate new concepts
The Mars Pathfinder Mission is developing a small, low cost and mass vehicle that demonstrates interplanetary cruise, entry, descent, and upright landing systems for use in future missions.
The primary objective of the CLARREO Pathfinder (CPF) mission is to demonstrate essential measurement technologies to enable highly accurate decadal change observations traceable on-orbit to SI standards. Another important objective of the CPF is to demonstrate inter-calibration with the VIIRS sensor and to show that such high-accuracy reference inter-calibration is achievable. To satisfy this requirement, it is important to understand and quantify uncertainties in VIIRS sensor measurements. Based on prelaunch test results, the reflective solar bands of both SNPP and NOAA-20 VIIRS have exhibited polarization sensitivities in the shortest wavelength bands, with an unexpectedly larger sensitivity observed for NOAA-20 VIIRS, particularly in bands M1 to M4. In this study, we use VIIRS Level-1B reflectance data collected over the Pseudo-Invariant Calibration Sites over North African desert region to examine the polarization associated uncertainty for these four bands. Impact due to BRDF on the reflectance data is considered by comparing baseline results obtained from the same viewing and solar zenith angles under relatively low polarization sensitivity. Impact due to detector relative difference in polarization sensitivity is examined by normalizing reflectances by the value of the middle detector. Results of this study provide useful information on VIIRS uncertainty contribution due to polarization when conducting CPF and VIIRS inter-calibration.
The Martian outflow channels comprise some of the largest known channels in the Solar System. Remote-sensing investigations indicate that cataclysmic floods likely excavated the channels ~3.4 Ga. Previous studies show that, in the southern circum-Chryse region, their flooding pathways include hundreds of kilometers of channel floors with upward gradients. However, the impact of the reversed channel-floor topography on the cataclysmic floods remains uncertain. Here, we show that these channel floors occur within a vast basin, which separates the downstream reaches of numerous outflow channels from the northern plains. Consequently, floods propagating through these channels must have ponded, producing an inland sea, before reaching the northern plains as enormous spillover discharges. The resulting paleohydrological reconstruction reinterprets the 1997 Pathfinder landing site as part of a marine spillway, which connected the inland sea to a hypothesized northern plains ocean. Our flood simulation shows that the presence of the sea would have permitted the propagation of low-depth floods beyond the areas of reversed channel-floor topography. These results explain the formation at the landing site of possible fluvial features indicative of flow depths at least an order of magnitude lower than those apparent from the analyses of orbital remote-sensing observations.
Non-recurrent short-term variations of the galactic cosmic-ray (GCR) flux above 70 MeV n−1 were observed between 2016 February 18 and 2017 July 3 on board the European Space Agency LISA Pathfinder (LPF) mission orbiting around the Lagrange point L1 at 1.5 × 106 km from Earth. The energy dependence of three Forbush decreases is studied and reported here. A comparison of these observations with others carried out in space down to the energy of a few tens of MeV n−1 shows that the same GCR flux parameterization applies to events of different intensity during the main phase. FD observations in L1 with LPF and geomagnetic storm occurrence are also presented. Finally, the characteristics of GCR flux non-recurrent variations (peaks and depressions) of duration <2 days and their association with interplanetary structures are investigated. It is found that, most likely, plasma compression regions between subsequent corotating high-speed streams cause peaks, while heliospheric current sheet crossing causes the majority of the depressions.
Non-recurrent short-term variations of the galactic cosmic-ray (GCR) flux above 70 MeV n(exp −1) were observed between 2016 February 18 and 2017 July 3 on board the European Space Agency LISA Pathfinder (LPF) mission orbiting around the Lagrange point L1 at 1.5 × 10 (exp 6) km from Earth. The energy dependence of three Forbush decreases is studied and reported here. A comparison of these observations with others carried out in space down to the energy of a few tens of MeV n(exp −1) shows that the same GCR flux parameterization applies to events of different intensity during the main phase. FD observations in L1 with LPF and geomagnetic storm occurrence are also presented. Finally, the characteristics of GCR flux non-recurrent variations (peaks and depressions) of duration <2 days and their association with interplanetary structures are investigated. It is found that, most likely, plasma compression regions between subsequent corotating high-speed streams cause peaks, while heliospheric current sheet crossing causes the majority of the depressions.
LISA Pathfinder (LPF) was a technology pioneering mission designed to test key technologies required for gravitational wave detection in space. In the low frequency regime (milliHertz and below), where space-based gravitational wave observatories will operate, temperature fluctuations play a crucial role since they can couple into the interferometric measurement and the test masses’ free-fall accuracy in many ways. A dedicated temperature measurement subsystem, with noise levels in 10 μKHz −1/2 down to 1 mHz was part of the diagnostics unit onboard LPF. In this paper we report on the temperature measurements throughout mission operations, characterize the thermal environment, estimate transfer functions between different locations, and report temperature stability (and its time evolution) at frequencies as low as 10 μHz, where typically values around 1KHz −1/2 were measured.
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder (CPF) mission consists of a high accuracy reflected solar spectrometer that will take measurements from the International Space Station for one year starting in 2023. CPF will demonstrate that its novel on-orbit absolute calibration approaches are capable of achieving 0.3% (1-sigma) radiometric uncertainty. Additionally, using its two-axis pointing gimbal which enables nearly-concurrent measurements matching look angles with other orbiting sensors, CPF will demonstrate a novel inter-calibration approach by inter-calibrating CERES and VIIRS. CPF is currently in its Final Design and Fabrication Stage and recently passed its Critical Design Review.
We report on the first subpicometer interferometer flown in space. It was part of ESA’s Laser Interferometer Space Antenna (LISA) Pathfinder mission and performed the fundamental measurement of the positional and angular motion of two free-falling test masses. The interferometer worked immediately, stably, and reliably from switch on until the end of the mission with exceptionally low residual noise of 32.0 (+2.4, −1.7) fm/(√Hz), significantly better than required. We present an upper limit for the sensor performance at millihertz frequencies and a model for the measured sensitivity above 200 mHz.
The Climate Absolute Radiance and Refractivity Observatory Pathfinder (CPF) mission on the International Space Station (ISS) will provide, for the first-time, an SI-traceable on-orbit calibration reference with a reflectance uncertainty of 0.3% (1 sigma). One major mission objective is to demonstrate the capability of transferring CPF’s radiometric accuracy to other satellite-based instruments, such as Clouds and Earth's Radiant Energy System (CERES) and Visible Infrared Imaging Radiometer Suite (VIIRS) on NOAA-20. CPF inter-calibration measurements will be planned to obtain inter-calibration samples that closely match satellite-based target sensor observations in time, space, angle, and wavelength. The inter-calibration event observations cover a wide range of viewing geometry angles with potential angular mismatch between CPF and the target sensors which can introduce non-negligible errors against the mission’s inter-calibration uncertainty budget. We will introduce the CPF approach to adjust for angular mismatch differences, thereby reducing the incurred uncertainties to within the inter-calibration uncertainty budget. The angular adjustment algorithm has been developed and validated based on the high-fidelity simulations of the CPF spectra using the Principal Component based Radiative Transfer Model (PCRTM). The implementation of the algorithm on event simulation data and the characterization for the angular adjustment uncertainty will be presented.
The Pathfinding for Airspace with Autonomous Vehicles (PAAV) project is investigating how to integrate increasingly autonomous aircraft into the current air traffic management system. The project aims to help develop airspace procedures and technologies that are scalable to future autonomous operations. The purpose of this brief is to inform a working group on past and future PAAV efforts. The working group specializes in "m:N" operations, which refers to remote operations where one or more ground-based pilots cooperatively control multiple unmanned aircraft. The PAAV team will detail an upcoming tabletop exercise that is designed to elicit feedback from subject matter experts on current barriers to m:N operations for unmanned cargo operations and potential solutions to those obstacles. The working group will be given an opportunity to provide feedback on the objectives and methodology to be used in the PAAV tabletop exercise.
The LISA Pathfinder (LPF) mission succeeded outstandingly in demonstrating key technologicalaspects of future space-borne gravitational-wave detectors, such as the Laser Interferometer SpaceAntenna (LISA). Specifically, LPF demonstrated with unprecedented sensitivity the measurementof the relative acceleration of two free-falling cubic test masses. Although most disruptive non-gravitational forces have been identified and their effects mitigated through a series of calibrationprocesses, some faint transient signals of yet unexplained origin remain in the measurements. If theyappear in the LISA data, these perturbations (also called glitches) could skew the characterizationof gravitational-wave sources or even be confused with gravitational-wave bursts. For the firsttime, we provide a comprehensive census of LPF transient events. Our analysis is based on aphenomenological shapelet model allowing us to derive simple statistics about the physical featuresof the glitch population. We then implement a generator of synthetic glitches designed to be usedfor subsequent LISA studies, and perform a preliminary evaluation of the effect of the glitches onfuture LISA data analyses.
Supported by NASA’s Earth Science Technology Office (ESTO), a new lidar transmitter system is developed under the Wind-Space Pathfinder coherent wind lidar project. It is an efficient Ho:LuLiF master oscillator power amplifier system (MOPA) that is capable of generating 15 watts power and 180 ns pulse width at 200 Hz PRF with excellent beam quality. The laser is injection seeded to provide stable single longitudinal frequency output. The laser beam polarization can be switched between “S” and “P” alternatively. Thus, the “S” and “P” beams can be directed to two separate telescopes at different directions to provide true horizontal wind measurement without a moving part in the lidar system. The laser power, pulse width and beam quality fulfill the space lidar system’s figure-of-merit (FOM) and measurement accuracy requirements.
Supported by NASA’s Earth Science Technology Office (ESTO), a new lidar transmitter system is developed under the Wind-Space Pathfinder coherent wind lidar project. It is an efficient Ho:LuLiF master oscillator power amplifier system (MOPA) that is capable of generating 15 watts power and 180 ns pulse width at 200 Hz PRF with excellent beam quality. The laser is injection seeded to provide stable single longitudinal frequency output. The laser beam polarization can be switched between “S” and “P” alternatively. Thus, the “S” and “P” beams can be directed to two separate telescopes at different directions to provide true horizontal wind measurement without a moving part in the lidar system. The laser power, pulse width and beam quality fulfill the space lidar system’s figure-of-merit (FOM) and measurement accuracy requirements.
The high-accuracy Earth-reflected solar spectral radiances from CLARREO Pathfinder (CPF) will serve as in-orbit benchmark measurements for intercalibrating other satellite imagers. The CPF team is developing a state-of-the-art intercalibration method to calibrate the shortwave channel (300-5000 nm) of the CERES instrument against the CPF reference with an uncertainty of 0.3%. Because the CPF instrument only covers spectral range from 350 nm to 2300 nm, the team has developed a spectral extension method to fill in the gaps between the spectral domains of CPF and the CERES shortwave channel. The method solely relies on using the hyperspectral information from the CPF wavelengths to predict the radiances below 350 nm and above 2300 nm. To quantify the relationship between the CPF spectrum and the non-overlapping portions of the spectrum between CPF and CERES, the team has simulated a large ensemble of spectra that cover the spectral range for both CPF and CERES. A hyperspectral bidirectional reflectance model for land surface based on thousands of measured land surface reflectance has been developed. This land surface model as well as the Cox-Munk model for ocean surface are used in the spectral gap filling. Various water/ice clouds, aerosols, atmosphere profiles and surfaces were used to simulate Earth-reflected radiances from 200 nm to 15 um under different solar and sensor geometries. The targeted uncertainty for the CPF-extended broadband CERES radiances is less than 0.1%. The previously derived training spectra were updated to replace the Kurucz solar irradiance model with the TSIS-1 Hybrid Solar Reference Spectrum. The influence of the scalar assumption in radiative transfer model equations on the uncertainty in estimating the broadband radiances was also investigated.
NASA's Pathfinding for Airspace with Autonomous Vehicles (PAAV) sub-project investigates procedures and technologies to facilitate seamless integration of future UAS operations into the NAS. The Tabletop 4 activity solicited subject matter expertise to identify solutions to the potential challenges expected when the remote pilot-to-vehicle ratio scales from 1:1 to m:N, where one or more ground-based pilots control multiple uncrewed aircraft. This report details the method and results of the PAAV Tabletop 4 activity.