2,483 research outputs found
Verifying timestamps of occultation observation systems
We describe an image timestamp verification system to determine the exposure
timing characteristics and continuity of images made by an imaging camera and
recorder, with reference to Coordinated Universal Time (UTC). The original use
was to verify the timestamps of stellar occultation recording systems, but the
system is applicable to lunar flashes, planetary transits, sprite recording, or
any area where reliable timestamps are required. The system offers good
temporal resolution (down to 2 msec, referred to UTC) and provides exposure
duration and interframe dead time information. The system uses inexpensive,
off-the- shelf components, requires minimal assembly and requires no
high-voltage components or connections. We also describe an application to load
FITS (and other format) image files, which can decode the verification image
timestamp. Source code, wiring diagrams and built applications are provided to
aid the construction and use of the device.Comment: 10 pages, 7 figures, accepted to Publications of the Astronomical
Society of Australia (PASA
TriG - A GNSS Precise Orbit and Radio Occultation Space Receiver
The GPS radio occultation (RO) technique [1] produces
measurements in the ionosphere and neutral atmosphere
[2] that contribute to monitoring space weather and climate
change; and improving operational weather prediction.
The high accuracy of RO soundings, traceable to SI standards,
makes them ideal climate benchmark observations. For
weather applications, RO observations improve the accuracy
of weather forecasts by providing temperature and moisture
profiles of sub-km vertical resolution, over land and ocean
and in the presence of clouds.
JPL is currently flying a handful of RO instruments [3] on
various satellites in Low Earth Orbit (LEO). Although these
receivers have served to pioneer occultation measurements,
various advances in technology and understanding of the RO
technique along with availability of new signals from GPS and
other GNSS satellites allow us to design an improved next
generation space-based Precise Orbit Determination (POD)
and RO receiver, the TriG receiver. The paper describes the
architecture and implementation of the JPL TriG receiver as
well as results obtained with a prototype receiver demonstrating
key technologies necessary for a next-generation space
science receiver
A digital video system for observing and recording occultations
Stellar occultations by asteroids and outer solar system bodies can offer
ground based observers with modest telescopes and camera equipment the
opportunity to probe the shape, size, atmosphere and attendant moons or rings
of these distant objects. The essential requirements of the camera and
recording equipment are: good quantum efficiency and low noise, minimal dead
time between images, good horological faithfulness of the image time stamps,
robustness of the recording to unexpected failure, and low cost. We describe
the Astronomical Digital Video occultation observing and recording System
(ADVS) which attempts to fulfil these requirements and compare the system with
other reported camera and recorder systems. Five systems have been built,
deployed and tested over the past three years, and we report on three
representative occultation observations: one being a 9 +/-1.5 second
occultation of the trans-Neptunian object 28978 Ixion (mv=15.2) at 3 seconds
per frame, one being a 1.51 +/-0.017 second occultation of Deimos, the 12~km
diameter satellite of Mars, at 30 frames per second, and one being a 11.04
+/-0.4 second occultation, recorded at 7.5 frames per second, of the main belt
asteroid, 361 Havnia, representing a low magnitude drop (Dmv = 0.4)
occultation.Comment: 9 pages, 5 figures, 3 tables, accepted to Publications of the
Astronomical Society of Australia (PASA
GNSS transpolar earth reflectometry exploriNg system (G-TERN): mission concept
The global navigation satellite system (GNSS) Transpolar Earth Reflectometry exploriNg system (G-TERN) was proposed in response to ESA's Earth Explorer 9 revised call by a team of 33 multi-disciplinary scientists. The primary objective of the mission is to quantify at high spatio-temporal resolution crucial characteristics, processes and interactions between sea ice, and other Earth system components in order to advance the understanding and prediction of climate change and its impacts on the environment and society. The objective is articulated through three key questions. 1) In a rapidly changing Arctic regime and under the resilient Antarctic sea ice trend, how will highly dynamic forcings and couplings between the various components of the ocean, atmosphere, and cryosphere modify or influence the processes governing the characteristics of the sea ice cover (ice production, growth, deformation, and melt)? 2) What are the impacts of extreme events and feedback mechanisms on sea ice evolution? 3) What are the effects of the cryosphere behaviors, either rapidly changing or resiliently stable, on the global oceanic and atmospheric circulation and mid-latitude extreme events? To contribute answering these questions, G-TERN will measure key parameters of the sea ice, the oceans, and the atmosphere with frequent and dense coverage over polar areas, becoming a “dynamic mapper”of the ice conditions, the ice production, and the loss in multiple time and space scales, and surrounding environment. Over polar areas, the G-TERN will measure sea ice surface elevation (<;10 cm precision), roughness, and polarimetry aspects at 30-km resolution and 3-days full coverage. G-TERN will implement the interferometric GNSS reflectometry concept, from a single satellite in near-polar orbit with capability for 12 simultaneous observations. Unlike currently orbiting GNSS reflectometry missions, the G-TERN uses the full GNSS available bandwidth to improve its ranging measurements. The lifetime would be 2025-2030 or optimally 2025-2035, covering key stages of the transition toward a nearly ice-free Arctic Ocean in summer. This paper describes the mission objectives, it reviews its measurement techniques, summarizes the suggested implementation, and finally, it estimates the expected performance.Peer ReviewedPostprint (published version
Enhancing Job Scheduling of an Atmospheric Intensive Data Application
Nowadays, e-Science applications involve great deal of data to have more accurate analysis. One of its application domains is the Radio Occultation which manages satellite data. Grid Processing Management is a physical infrastructure geographically distributed based on Grid Computing, that is implemented for the overall processing Radio Occultation analysis. After a brief description of algorithms adopted to characterize atmospheric profiles, the paper presents an improvement of job scheduling in order to decrease processing time and optimize resource utilization. Extension of grid computing capacity is implemented by virtual machines in existing physical Grid in order to satisfy temporary job requests. Also scheduling plays an important role in the infrastructure that is handled by a couple of schedulers which are developed to manage data automaticall
Orographic and convective gravity waves above the Alps and Andes mountains during GPS radio occultation events – a case study
The significant distortions introduced in the measured atmospheric gravity wavelengths by soundings other than in vertical and horizontal directions, are discussed as a function of elevation angle of the sounding path and the gravity waves aspect ratio. Under- or overestimation of real vertical wavelengths during the measurement process depends basically on the value of these two parameters. The consequences of these distortions on the calculation of the energy and vertical flux of horizontal momentum are analyzed and discussed in the context of two experimental limb satellite setups: GPS-LEO radio occultations and TIMED/SABER measurements. Possible discrepancies previously found between the momentum flux calculated from satellite temperature profiles, on site and from model simulations, may, to a certain degree, be attributed to these distortions. A recalculation of previous momentum flux climatologies based on these considerations seems to be a difficult goal.Fil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería. Departamento de Ciencias Básicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Steiner, Andrea K.. Universidad de Graz; AustriaFil: de la Torre, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería. Departamento de Ciencias Básicas; ArgentinaFil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Llamedo Soria, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería. Departamento de Ciencias Básicas; ArgentinaFil: Cremades, Pablo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentin
Data intensive scientific analysis with grid computing
At the end of September 2009, a new Italian GPS receiver for radio occultation was launched from the Satish Dhawan Space Center (Sriharikota, India) on the Indian Remote Sensing OCEANSAT-2 satellite. The Italian Space Agency has established a set of Italian universities and research centers to implement the overall processing radio occultation chain. After a brief description of the adopted algorithms, which can be used to characterize the temperature, pressure and humidity, the contribution will focus on a method for automatic processing these data, based on the use of a distributed architecture. This paper aims at being a possible application of grid computing for scientific research
The 1998 November 14 Occultation of GSC 0622-00345 by Saturn. I. Techniques for Ground-Based Stellar Occultations
On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345.
We observed atmospheric immersion with NSFCAM at the National Aeronautics and
Space Administration's Infrared Telescope Facility on Mauna Kea, Hawaii.
Immersion occurred at 55.5\circ S planetocentric latitude. A 2.3 {\mu}m,
methane-band filter suppressed reflected sunlight. Atmospheric emersion and
ring data were not successfully obtained. We describe our observation,
light-curve production, and timing techniques, including improvements in
aperture positioning, removal of telluric scintillation effects, and timing.
Many of these techniques are known within the occultation community, but have
not been described in the reviewed literature. We present a light curve whose
signal-to-noise ratio per scale height is 267, among the best ground-based
signals yet achieved, despite a disadvantage of up to 8 mag in the stellar flux
compared to prior work.Comment: LaTeX/emulateapj, 6 pages, 3 figures. Online items: The FITS-format
light curve and the IDL code for the timing model are available from ApJ or
the lead autho
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