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NASA NTRS1992

Propagation effects for land mobile satellite systems: Overview of experimental and modeling results

Models developed and experiments performed to characterize the propagation environment associated with land mobile communication using satellites are discussed. Experiments were carried out with transmitters on stratospheric balloons, remotely piloted aircraft, helicopters, and geostationary satellites. This text is comprised of compiled experimental results for the expressed use of communications engineers, designers of planned Land Mobile Satellite Systems (LMSS), and modelers of propagation effects. The results presented here are mostly derived from systematic studies of propagation effects for LMSS geometries in the United States associated with rural and suburban regions. Where applicable, the authors also draw liberally from the results of other related investigations in Canada, Europe, and Australia. Frequencies near 1500 MHz are emphasized to coincide with frequency bands allocated for LMSS by the International Telecommunication Union, although earlier experimental work at 870 MHz is also included.

Goldhirsh, Julius↗

NASA NTRS1990

An overview of results derived from mobile-satellite propagation experiments

During the period 1983-1988, a series of Land Mobile Satellite Service (LMSS) propagation experiments were performed. These experiments were implemented with transmitters on stratospheric balloons, remotely piloted aircraft, helicopters, and geostationary satellites. The earlier experiments were performed at UHF (870 mega-Hz) and the latter at both L band (1.5 giga-Hz) and UHF. The general objective of the above tests was to assess the impairment to propagation caused by trees and terrain for predominantly suburban and rural regions where cellular communication services are impractical. This paper presents an overview of the results derived from the above experiments.

Goldhirsh, Julius↗

NASA NTRS2000

Stratospheric Sampling and In Situ Atmospheric Chemical Element Analysis During Meteor Showers: A Resource Study

Resources studies for asteroidal mining evaluation have depended historically on remote sensing analysis for chemical elements. During the November 1998 Leonids meteor shower, a stratospheric balloon and various low-density capture media were used to sample fragments from Comet Tempel-Tuttle debris during a peak Earth crossing. The analysis not only demonstrates how potential sampling strategies may improve the projections for metals or rare elements in astromining, but also benchmarks materials during low temperature (-60 F), high dessication environments as seen during atmospheric exposure. The results indicate high aluminum, magnesium and iron content for various sampled particles recovered, but generalization to the sporadic meteors expected from asteroidal sources will require future improvements in larger sampling volumes before a broad-use strategy for chemical analysis can be described. A repeat of the experimental procedure is planned for the November 1999 Leonids' shower, and various improvements for atmospheric sampling will be discussed.

Noever, David A.↗

NASA NTRS2001

Fabricating High Resolution Mirrors for Hand X-Ray Astronomy

We describe the fabrication process for producing high-resolution conical mirrors for hard x-ray astronomy. When flown aboard stratospheric balloons, these high-resolution reflective mirrors focus hard x-rays (10-70 keV) emitted from cosmic sources such as supernovae, neutron stars, and quasars onto imaging focal plane detectors. Focused hard x-ray images allow scientists to determine the elemental compositions, temperatures, magnetic fields, velocities, and gravitational fields of these celestial bodies. The fabrication process involves generating super-polished mandrels, mandrel metrology, mirror shell nickel electroforming, and mirror testing. Each mandrel is a cylinder consisting of two conical segments; each segment is approximately 305-mm long. Through precision grinding these mandrels before super polishing, we have achieved 30 arc seconds, half power diameter replicated mirrors. During a May 2001 high atmosphere balloon flight, these mirrors focused high energy x-rays from three different celestial sources. However, we seek to improve the angular resolutions of future mirror shells by a factor of two. To achieve this goal, we have begun single point diamond turning the mandrels before super polishing. This has allowed greater precision tolerances on mandrel surface roughness and axial figure errors before super polishing. Surface roughnesses before polishing have been reduced from approximately 60 nm to approximately 15 nm. The peak to valley axial figure profile errors have been reduced from approximately 1.0 micrometers to approximately 0.4 micrometers. We are currently in Phase 2 of the HERO (high energy replicated optics) program which entails the production of sixteen 6-m-focal-length mirror modules, each containing a nested array of 15 mirror shells of diameters ranging from 50-mm to 94-mm. This flight is slated for the fall of 2003.

Speegle, Chet O.↗

NASA NTRS2001

A High-Precision, Fast-Response Airborne CO2 Analyzer for In Situ Sampling From the Surface to the Middle Stratosphere

Two in situ CO2 analyzers have been developed for deployment on the NASA ER-2 aircraft and on stratospheric balloons. The ER-2 instrument has had more than 150 flights during 21 deployments from 1992 to 2000, resulting in a dataset with nearly pole-to-pole coverage that includes data from all seasons in both hemispheres except austral summer. In-flight calibrations show that the typical long-term (i.e. flight-to-flight) precision of the instruments is better than plus or minus 0.1 ppmv. The flight standards are traceable to standards held by the Scripps Institute of Oceanography and the National Oceanic and Atmospheric Administration's Climate Monitoring and Diagnostics Laboratory. The balloon instrument has had 8 balloon flights since September 1996, providing the first in situ observations of CO2 above approx. 21 km. In addition, the balloon instrument has been flown onboard a Cessna Citation II aircraft for sampling between the surface and 10 km. In this paper, the instrumentation and calibration procedures for both instruments are described in detail. An intercomparison of the two instruments during the Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) project showed that, on average, the instruments agreed to within 0.05 ppmv.

Daube, B. C., Jr.↗

NASA NTRS2002

Development of High Resolution Mirrors and Cd-Zn-Te Detectors for Hard X-ray Astronomy

We describe the fabrication and implementation of a high-resolution conical, grazing- incidence, hard X-ray (20-70 keV) telescope. When flown aboard stratospheric balloons, these mirrors are used to image cosmic sources such as supernovae, neutron stars, and quasars. The fabrication process involves generating super-polished mandrels, mirror shell electroforming, and mirror testing. The cylindrical mandrels consist of two conical segments; each segment is approximately 305 mm long. These mandrels are first, precision ground to within approx. 1.0 micron straightness along each conical segment and then lapped and polished to less than 0.5 micron straightness. Each mandrel segment is the super-polished to an average surface roughness of approx. 3.25 angstrom rms. By mirror shell replication, this combination of good figure and low surface roughness has enabled us to achieve 15 arcsec, confirmed by X-ray measurements in the Marshall Space Flight Center 102 meter test facility. To image the focused X-rays requires a focal plane detector with appropriate spatial resolution. For 15 arcsec optics of 6 meter focal length, this resolution must be around 200 microns. In addition, the detector must have a high efficiency, relatively high energy resolution, and low background. We are currently developing Cadmium-Zinc-Telluride fine-pixel detectors for this purpose. The detectors under study consist of a 16x16 pixel array with a pixel pitch of 300 microns and are 1 mm and 2 mm thick. At 60 keV, the measured energy resolution is around 2%.

Ramsey, Brian D.↗

NASA NTRS2003

Testing the Equivalence Principle in an Einstein Elevator: Detector Dynamics and Gravity Perturbations

We discuss specific, recent advances in the analysis of an experiment to test the Equivalence Principle (EP) in free fall. A differential accelerometer detector with two proof masses of different materials free falls inside an evacuated capsule previously released from a stratospheric balloon. The detector spins slowly about its horizontal axis during the fall. An EP violation signal (if present) will manifest itself at the rotational frequency of the detector. The detector operates in a quiet environment as it slowly moves with respect to the co-moving capsule. There are, however, gravitational and dynamical noise contributions that need to be evaluated in order to define key requirements for this experiment. Specifically, higher-order mass moments of the capsule contribute errors to the differential acceleration output with components at the spin frequency which need to be minimized. The dynamics of the free falling detector (in its present design) has been simulated in order to estimate the tolerable errors at release which, in turn, define the release mechanism requirements. Moreover, the study of the higher-order mass moments for a worst-case position of the detector package relative to the cryostat has led to the definition of requirements on the shape and size of the proof masses.

Hubbard, Dorthy↗

NASA NTRS2005

The Huygens Atmospheric Structure Instrument (HASI): Expected Results at Titan and Performance Verification in Terrestrial Atmosphere

The Huygens ASI is a multi-sensor package resulting from an international cooperation, it has been designed to measure the physical quantities characterizing Titan's atmosphere during the Huygens probe mission. On 14th January, 2005, HASI will measure acceleration, pressure, temperature and electrical properties all along the Huygens probe descent on Titan in order to study Titan s atmospheric structure, dynamics and electric properties. Monitoring axial and normal accelerations and providing direct pressure and temperature measurements during the descent, HASI will mainly contribute to the Huygens probe entry and trajectory reconstruction. In order to simulate the Huygens probe descent and verify HASI sensors performance in terrestrial environment, stratospheric balloon flight experiment campaigns have been performed, in collaboration with the Italian Space Agency (ASI). The results of flight experiments have allowed to determine the atmospheric vertical profiles and to obtain a set of data for the analysis of probe trajectory and attitude reconstruction.

Ferri, F.↗

NASA NTRS2012

Solar Simulation for the CREST Preflight Thermal-Vacuum Test at B-2

In June 2011, the multi-university sponsored Cosmic Ray Electron Synchrotron Telescope (CREST) has undergone thermal-vacuum qualification testing at the NASA Glenn Research Center (GRC), Plum Brook Station, Sandusky, Ohio. The testing was performed in the B-2 Space Propulsion Facility vacuum chamber. The CREST was later flown over the Antarctic region as the payload of a stratospheric balloon. Solar simulation was provided by a system of planar infrared lamp arrays specifically designed for CREST. The lamp arrays, in conjunction with a liquid-nitrogen-cooled cold wall, achieved the required thermal conditions for the qualification tests. The following slides accompanied the presentation of the report entitled Solar Simulation for the CREST Preflight Thermal-Vacuum Test at B-2, at the 27th Aerospace Testing Seminar, October 2012. The presentation described the test article, the test facility capability, the solar simulation requirements, the highlights of the engineering approach, and the results achieved. The presentation was intended to generate interest in the report and in the B-2 test facility.

Ziemke, Robert A.↗

NASA NTRS2013

Solar Simulation for the CREST Preflight Thermal-Vacuum Test at B-2

In June 2011, the multi-university sponsored Cosmic Ray Electron Synchrotron Telescope (CREST) has undergone thermal-vacuum qualification testing at the NASA Glenn Research Center (GRC), Plum Brook Station, Sandusky, Ohio. The testing was performed in the B- 2 Space Propulsion Facility vacuum chamber. The CREST was later flown over the Antarctic region as the payload of a stratospheric balloon. Solar simulation was provided by a system of planar infrared lamp arrays specifically designed for CREST. The lamp arrays, in conjunction with a liquid-nitrogen-cooled cryoshroud, achieved the required thermal conditions for the qualification tests. This report focuses on the design and analysis of the planar arrays based on first principles. Computational spreadsheets are included in the report.

Ziemke, Robert A.↗

NASA NTRS2015

Out of This World Science, Down to Earth Prices

The National Aeronautics and Space Administration (NASA), along with the rest of government and the nation have become increasing cost conscious in recent years. This has resulted in renewed efforts at finding ways to do more with less. Planetary science is no exception. The 2013 Decadal Survey for Planetary Science made great efforts to understand the costs of proposed missions. The community has been asked to develop more affordable versions of mission concepts, especially in the flagship category. Many in the community continue to encourage NASA to prioritize lower cost missions at a more frequent cadence over fewer but larger missions. This presentation discusses a new tool in the planetary science arsenal to achieve a broad set of planetary science questions at costs that are lower, and in some cases dramatically lower, than other options in the past. Technology advances in pointing systems and the growing capabilities of stratospheric balloons, such as the ultra-long duration flights, have caught the attention of many in the planetary science community. A workshop was held in January 2012 to help planetary scientists and NASA better understand the capabilities of balloon borne platforms, along with their strengths and limitations. Perhaps most importantly, the workshop focused on the potential science that could be achieved. The science and engineering participants discussed what, if any, science can be achieved and why or how balloon platforms would offer an advantage. Since that first workshop, not only have further discussions and studies occurred within the community, but demonstration missions have been flown with compelling results. These balloon missions have shown that the science envisioned can indeed be achievable, that balloon platforms do offer some unique advantages; and that repeated flights can be implemented at relatively low cost. The presentation briefly summarizes the potential science and the characteristics of a balloon based observatory that make it desirable for some science investigations. The recent missions are described along with some of their challenges and achievements. Finally, a brief summary of options moving forward are considered.

Planetary Science↗

NASA NTRS2016

Cubesat Application for Planetary Entry (CAPE) Missions: Micro-Return Capsule (MIRCA)

The Cubesat Application for Planetary Entry Missions (CAPE) concept describes a high-performing Cubesat system which includes a propulsion module and miniaturized technologies capable of surviving atmospheric entry heating, while reliably transmitting scientific and engineering data. The Micro Return Capsule (MIRCA) is CAPE's first planetary entry probe flight prototype. Within this context, this paper briefly describes CAPE's configuration and typical operational scenario, and summarizes ongoing work on the design and basic aerodynamic characteristics of the prototype MIRCA vehicle. CAPE not only opens the door to new planetary mission capabilities, it also offers relatively low-cost opportunities especially suitable to university participation. In broad terms, CAPE consists of two main functional components: the "service module" (SM), and "CAPE's entry probe" (CEP). The SM contains the subsystems necessary to support vehicle targeting (propulsion, ACS, computer, power) and the communications capability to relay data from the CEP probe to an orbiting "mother-ship". The CEP itself carries the scientific instrumentation capable of measuring atmospheric properties (such as density, temperature, composition), and embedded engineering sensors for Entry, Descent, and Landing (EDL). The first flight of MIRCA was successfully completed on 10 October 2015 as a "piggy-back" payload onboard a NASA stratospheric balloon launched from Ft. Sumner, NM.

Cubesat↗

NASA NTRS2016

Characterization of the RaD-X Mission Instruments

The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission, launched on 25 September 2015, provided dosimetric measurements above the Pfotzer maximum. The goal of taking these measurements is to improve aviation radiation models by providing a characterization of cosmic ray primaries, which are the source of radiation exposure at aviation altitudes. The RaD-X science payload consists of four instruments. The main science instrument is a tissue-equivalent proportional counter (TEPC). The other instruments consisted of three solid state silicon dosimeters: Liulin, Teledyne total ionizing dose (TID) and RaySure detectors. To properly interpret the measurements, it is necessary to evaluate how the payload affects the radiation environment of the detectors. In addition, it is necessary to evaluate how the detectors react to the different particles impacting them. We present the results of the Geant-4 simulations of the interaction of the different radiations with the payload and the instruments. We show how it affect the measurements, and which instruments are better suited for future missions

Gronoff, Guillaume↗

NASA NTRS2016

Cosmic Radiation Dose Measurements from the RaD-X Flight Campaign

The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission obtained measurements for improving the understanding of cosmic radiation transport in the atmosphere and human exposure to this ionizing radiation field in the aircraft environment. The value of dosimetric measurements from the balloon platform is that they can be used to characterize cosmic ray primaries, the ultimate source of aviation radiation exposure. In addition, radiation detectors were flown to assess their potential application to long-term, continuous monitoring of the aircraft radiation environment. The RaD-X balloon was successfully launched from Fort Sumner, New Mexico (34.5 degrees North, 104.2 degrees West) on 25 September 2015. Over 18 hours of flight data were obtained from each of the four different science instruments at altitudes above 20 kilometers. The RaD-X balloon flight was supplemented by contemporaneous aircraft measurements. Flight-averaged dosimetric quantities are reported at seven altitudes to provide benchmark measurements for improving aviation radiation models. The altitude range of the flight data extends from commercial aircraft altitudes to above the Pfotzer maximum where the dosimetric quantities are influenced by cosmic ray primaries. The RaD-X balloon flight observed an absence of the Pfotzer maximum in the measurements of dose equivalent rate.

Mertens, Christopher J.↗

NASA NTRS2016

Overview of the Radiation Dosimetry Experiment (RaD-X) Flight Mission

The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission addresses the need to reduce the uncertainty in predicting human exposure to cosmic radiation in the aircraft environment. Measurements were taken that characterize the dosimetric properties of cosmic ray primaries, the ultimate source of aviation radiation exposure, and the cosmic ray secondary radiations that are produced and transported to aviation altitudes. In addition, radiation detectors were flown to assess their potential application to long-term, continuous monitoring of the aircraft radiation environment. RaD-X was successfully launched from Fort Sumner, New Mexico (34.5 N, 104.2 W), on 25 September 2015. Over 18 h of science data were obtained from a total of four different type dosimeters at altitudes above 20 km. The RaD-X flight mission was supported by laboratory radiation exposure testing of the balloon flight dosimeters and also by coordinated radiation measurements taken on ER-2 and commercial aircraft. This paper provides the science background and motivation for the RaD-X flight mission, a brief description of the balloon flight profile and the supporting aircraft flights, and a summary of the articles included in the RaD-X special collection and their contributions to the science goals of the RaD-X mission.

Mertens, Christopher J.↗

NASA NTRS2023

Study of Pairwise Deconfliction Metrics to Analyze Air Traffic Complexity in Upper Class E Airspace

Upper Class E Traffic Management (ETM) is envisioned to cooperatively facilitate operations of a diverse set of aerial vehicles, such as high-altitude long-endurance fixed-wing unmanned aircraft (low-speed and high-speed), high-altitude platforms, airships, stratospheric balloons, supersonic unmanned and commercial aircraft, etc., with a wide variety of mission types, performance characteristics, communication, navigation and surveillance capabilities, maneuverability, and on-board avionics in the National Airspace System (NAS) ’above’ 60,000 feet above mean sea level, without an active and direct control from human air traffic controllers. A diverse mixture of aerial vehicle types creates significant challenges in understanding air traffic complexity, which may not correlate strongly with air traffic density. One key step for determining air traffic complexity in upper class E airspace is to first understand pairwise deconfliction metrics such as reachability, reserve area, and reserve flight time for each pair of unique aerial vehicle types under potential conflict. Therefore, pairwise deconfliction metrics are first defined, and analytical equations are derived for conflict resolution using the heading change maneuver. Next, case studies are performed to analyze deconfliction metrics to avoid secondary conflicts in upper class E airspace. The study shows that pairwise deconfliction metrics are functions of maneuverability, performance characteristics, uncertainty in position and velocity, heading angle change, and conflict angle of aerial vehicles. The next step for this research is to build a mathematical model for air traffic complexity using pairwise deconfliction metrics and validate it in an upper Class E simulation environment.

Airspace Complexity↗

NASA NTRSDate not supplied

Study of Pairwise Deconfliction Metrics to Analyze Air Traffic Complexity in Upper Class E Airspace

Airspace Complexity↗

NASA NTRSDate not supplied

Design and Technology Maturation of the Stratospheric Projectile Experiment of Entry Dynamics

A new technique for obtaining stratospheric free-flight dynamics data for atmospheric entry capsules is described. The Stratospheric Projectile Experiment of Entry Dynamics (SPEED) represents a new approach to characterizing the free-flight dynamics of vehicles in the supersonic and transonic regime of flight. The SPEED test architecture leverages a stratospheric balloon and 3D-printed flight system in a novel two-stage configuration to deliver test articles to supersonic conditions in the atmosphere which achieve dynamic similitude with a full-scale vehicle. Designed to address the limitations of existing test facilities, SPEED captures the complete time evolution of a vehicle’s dynamic state while producing a statistically significant number of observed flight trajectories to address the stochastic nature of the wake-driven dynamic stability phenomenon. SPEED was developed over two years at NASA Ames Research Center. This presentation describes the motivation for a new test architecture, operational constraints and achievable flight test envelopes, the design, and development of the SPEED concept.

Dynamic Stability↗