Modeling the variations of Dose Rate measured by RAD during the first MSL Martian year: 2012-2014

The Radiation Assessment Detector (RAD), on board Mars Science Laboratory's (MSL) rover Curiosity, measures the {energy spectra} of both energetic charged and neutral particles along with the radiation dose rate at the surface of Mars. With these first-ever measurements on the Martian surface, RAD observed several effects influencing the galactic cosmic ray (GCR) induced surface radiation dose concurrently: [a] short-term diurnal variations of the Martian atmospheric pressure caused by daily thermal tides, [b] long-term seasonal pressure changes in the Martian atmosphere, and [c] the modulation of the primary GCR flux by the heliospheric magnetic field, which correlates with long-term solar activity and the rotation of the Sun. The RAD surface dose measurements, along with the surface pressure data and the solar modulation factor, are analysed and fitted to empirical models which quantitatively demonstrate} how the long-term influences ([b] and [c]) are related to the measured dose rates. {Correspondingly we can estimate dose rate and dose equivalents under different solar modulations and different atmospheric conditions, thus allowing empirical predictions of the Martian surface radiation environment

Recurrent geomagnetic storms and relativistic electron enhancements in the outer magnetosphere: ISTP coordinated measurements

New, coordinated measurements from the International Solar-Terrestrial Physics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth\u27s magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent geomagnetic activity. It is concluded that even during extremely quiet solar conditions (sunspot minimum) there are discernible coronal holes and resultant solar wind streams which can produce intense magnetospheric particle acceleration. As a practical consequence of this Sun-Earth connection, it is noted that a long-lasting E\u3e1MeV electron event in late March 1996 appears to have contributed significantly to a major spacecraft (Anik E1) operational failure

A Testbed for Developing and Evaluating GNSS Signal Authentication Techniques

An experimental testbed has been created for developing and evaluating Global Navigation Satellite System (GNSS) signal authentication techniques. The testbed advances the state of the art in GNSS signal authentication by subjecting candidate techniques to the strongest publicly-acknowledged GNSS spoofing attacks. The testbed consists of a real-time phase-coherent GNSS signal simulator that acts as spoofer, a real-time softwaredefined GNSS receiver that plays the role of defender, and post-processing versions of both the spoofer and defender. Two recently-proposed authentication techniques are analytically and experimentally evaluated: (1) a defense based on anomalous received power in a GNSS band, and (2) a cryptographic defense against estimation-and-replay-type spoofing attacks. The evaluation reveals weaknesses in both techniques; nonetheless, both significantly complicate a successful GNSS spoofing attackAerospace Engineering and Engineering Mechanic

Space and surface power for the space exploration initiative: Results from project outreach

The analysis and evaluations of the Space and Surface Power panel, one of eight panels created by RAND to screen and analyze submissions to the Space Exploration Initiative (SEI) Outreach Program, is documented. In addition to managing and evaluating the responses, or submissions, to this public outreach program, RAND conducted its own analysis and evaluation relevent to SEI mission concepts, systems, and technologies. The Power panel screened and analyzed submissions for which a substantial portion of the concepts involved power generation sources, transmission, distribution, thermal management, and handling of power (including conditioning, conversion, packaging, and enhancements in system components). A background discussion of the areas the Power panel covered and the issues the reviewers considered pertinent to the analysis of power submissions are presented. An overview of each of the highest-ranked submissions and then a discussion of these submissions is presented. The results of the analysis is presented

Towards Other Planetary Systems (TOPS): A technology needs identification workshop

The workshop identified a strong commonality between the technology needs for NASA's TOPS program and the technology needs that were identified for NASA's astrophysics program through its Astrotech 21 survey. The workshop encourages NASA to have the Solar System Exploration and Astrophysics Div. work cooperatively to share in technology studies that are common to both programs, rather than to conduct independent studies. It was also clear, however, that there are technology needs specific to TOPS, and these should be pursued by the Solar System Exploration Div. There are two technology areas that appear to be particularly critical to realizing the ultimate performance that is being sought under the TOPS program, these areas are metrology and optics. The former is critical in calibration and verification of instrument performance, while the latter is needed to provide optical systems of sufficient quality to conduct a search for and characterization of other planetary systems at the more extreme levels of performance identified in TOPS program

A multiple thruster array for 30-cm thrusters

A 3.0 m diameter chamber of the 7.6 m diameter by 21.4 m long vacuum tank was modified to permit testing of an array of up to six 30-cm thrusters with a variety of laboratory and thermal vacuum breadboard power systems. A primary objective of the Multiple Thruster Array (MTA) program is to assess the impact of multiple thruster operation on individual thruster and power processor requirements. The areas of thruster startup, steady-state operation, throttling, high voltage recycle, thrust vectoring, and shutdown are of special concern. The results of initial tests are reported