21,001 research outputs found
Autonomous navigation accuracy using simulated horizon sensor and sun sensor observations
A relatively simple autonomous system which would use horizon crossing indicators, a sun sensor, a quartz oscillator, and a microprogrammed computer is discussed. The sensor combination is required only to effectively measure the angle between the centers of the Earth and the Sun. Simulations for a particular orbit indicate that 2 km r.m.s. orbit determination uncertainties may be expected from a system with 0.06 deg measurement uncertainty. A key finding is that knowledge of the satellite orbit plane orientation can be maintained to this level because of the annual motion of the Sun and the predictable effects of Earth oblateness. The basic system described can be updated periodically by transits of the Moon through the IR horizon crossing indicator fields of view
Remote-sensing Characterisation of Major Solar System Bodies with the Twinkle Space Telescope
Remote-sensing observations of Solar System objects with a space telescope
offer a key method of understanding celestial bodies and contributing to
planetary formation and evolution theories. The capabilities of Twinkle, a
space telescope in a low Earth orbit with a 0.45m mirror, to acquire
spectroscopic data of Solar System targets in the visible and infrared are
assessed. Twinkle is a general observatory that provides on demand observations
of a wide variety of targets within wavelength ranges that are currently not
accessible using other space telescopes or that are accessible only to
oversubscribed observatories in the short-term future. We determine the periods
for which numerous Solar System objects could be observed and find that Solar
System objects are regularly observable. The photon flux of major bodies is
determined for comparison to the sensitivity and saturation limits of Twinkle's
instrumentation and we find that the satellite's capability varies across the
three spectral bands (0.4-1, 1.3-2.42, and 2.42-4.5{\mu}m). We find that for a
number of targets, including the outer planets, their large moons, and bright
asteroids, the model created predicts that with short exposure times,
high-resolution spectra (R~250, {\lambda}
2.42{\mu}m) could be obtained with signal-to-noise ratio (SNR) of >100 with
exposure times of <300s
Differential correction and preliminary orbit determination for lunar satellite orbits
Differential correction and preliminary orbit calculation for lunar satellite orbit
Monte Carlo simulation of an experiment looking for radiative solar neutrino decays
We analyse the possibility of detecting visible photons from a hypothetical
radiative decay of solar neutrinos. Our study is focused on the simulation of
such measurements during total solar eclipses and it is based on the BP2000
Standard Solar Model and on the most recent experimental information concerning
the neutrino properties.Comment: 13 pages, 10 figures, accepted by Astropart. Phy
Future Astronomical Observatories on the Moon
Papers at a workshop which consider the topic astronomical observations from a lunar base are presented. In part 1, the rationale for performing astronomy on the Moon is established and economic factors are considered. Part 2 includes concepts for individual lunar based telescopes at the shortest X-ray and gamma ray wavelengths, for high energy cosmic rays, and at optical and infrared wavelengths. Lunar radio frequency telescopes are considered in part 3, and engineering considerations for lunar base observatories are discussed in part 4. Throughout, advantages and disadvantages of lunar basing compared to terrestrial and orbital basing of observatories are weighted. The participants concluded that the Moon is very possibly the best location within the inner solar system from which to perform front-line astronomical research
Prospects in the orbital and rotational dynamics of the Moon with the advent of sub-centimeter lunar laser ranging
Lunar Laser Ranging (LLR) measurements are crucial for advanced exploration
of the laws of fundamental gravitational physics and geophysics. Current LLR
technology allows us to measure distances to the Moon with a precision
approaching 1 millimeter. As NASA pursues the vision of taking humans back to
the Moon, new, more precise laser ranging applications will be demanded,
including continuous tracking from more sites on Earth, placing new CCR arrays
on the Moon, and possibly installing other devices such as transponders, etc.
Successful achievement of this goal strongly demands further significant
improvement of the theoretical model of the orbital and rotational dynamics of
the Earth-Moon system. This model should inevitably be based on the theory of
general relativity, fully incorporate the relevant geophysical processes, lunar
librations, tides, and should rely upon the most recent standards and
recommendations of the IAU for data analysis. This paper discusses methods and
problems in developing such a mathematical model. The model will take into
account all the classical and relativistic effects in the orbital and
rotational motion of the Moon and Earth at the sub-centimeter level. The new
model will allow us to navigate a spacecraft precisely to a location on the
Moon. It will also greatly improve our understanding of the structure of the
lunar interior and the nature of the physical interaction at the core-mantle
interface layer. The new theory and upcoming millimeter LLR will give us the
means to perform one of the most precise fundamental tests of general
relativity in the solar system.Comment: 26 pages, submitted to Proc. of ASTROCON-IV conference (Princeton
Univ., NJ, 2007
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