3 research outputs found
Helium-3 Mining Aerostats in the Atmospheres of the Outer Planets
Imagine an interplanetary future where: a) d-He3 fusion produces most of Earth s energy needs without radioactivity or carbon emissions; b) Space transportation has been revolutionized by an efficient fusion propulsion system with exhaust velocity up to 0.088 c; c) Space commerce is stimulated by the existence of an interplanetary cargo worth $3-M a kilogram; and d) Unmanned probes travel to the nearest star systems with flight times less than a human lifetime
Flagging and Correction of Pattern Noise in the Kepler Focal Plane Array
In order for Kepler to achieve its required less than 20 PPM photometric precision for magnitude 12 and brighter stars, instrument-induced variations in the CCD readout bias pattern (our "2D black image"), which are either fixed or slowly varying in time, must be identified and the corresponding pixels either corrected or removed from further data processing. The two principle sources of these readout bias variations are crosstalk between the 84 science CCDs and the 4 fine guidance sensor (FGS) CCDs and a high frequency amplifier oscillation on less than 40% of the CCD readout channels. The crosstalk produces a synchronous pattern in the 2D black image with time-variation observed in less than 10% of individual pixel bias histories. We will describe a method of removing the crosstalk signal using continuously-collected data from masked and over-clocked image regions (our "collateral data"), and occasionally-collected full-frame images and reverse-clocked readout signals. We use this same set to detect regions affected by the oscillating amplifiers. The oscillations manifest as time-varying moir pattern and rolling bands in the affected channels. Because this effect reduces the performance in only a small fraction of the array at any given time, we have developed an approach for flagging suspect data. The flags will provide the necessary means to resolve any potential ambiguity between instrument-induced variations and real photometric variations in a target time series. We will also evaluate the effectiveness of these techniques using flight data from background and selected target pixels
KEPLER's First Rocky Planet: Kepler-10b
NASA's Kepler Mission uses transit photometry to determine the frequency of
earth-size planets in or near the habitable zone of Sun-like stars. The mission
reached a milestone toward meeting that goal: the discovery of its first rocky
planet, Kepler-10b. Two distinct sets of transit events were detected: 1) a 152
+/- 4 ppm dimming lasting 1.811 +/- 0.024 hours with ephemeris
T[BJD]=2454964.57375+N*0.837495 days and 2) a 376 +/- 9 ppm dimming lasting
6.86 +/- 0.07 hours with ephemeris T[BJD]=2454971.6761+N*45.29485 days.
Statistical tests on the photometric and pixel flux time series established the
viability of the planet candidates triggering ground-based follow-up
observations. Forty precision Doppler measurements were used to confirm that
the short-period transit event is due to a planetary companion. The parent star
is bright enough for asteroseismic analysis. Photometry was collected at
1-minute cadence for >4 months from which we detected 19 distinct pulsation
frequencies. Modeling the frequencies resulted in precise knowledge of the
fundamental stellar properties. Kepler-10 is a relatively old (11.9 +/- 4.5
Gyr) but otherwise Sun-like Main Sequence star with Teff=5627 +/- 44 K,
Mstar=0.895 +/- 0.060 Msun, and Rstar=1.056 +/- 0.021 Rsun. Physical models
simultaneously fit to the transit light curves and the precision Doppler
measurements yielded tight constraints on the properties of Kepler-10b that
speak to its rocky composition: Mpl=4.56 +/- 1.29 Mearth, Rpl=1.416 +/- 0.036
Rearth, and density=8.8 +/- 2.9 gcc. Kepler-10b is the smallest transiting
exoplanet discovered to date.Comment: Accepted, Astrophysical Journal, November 25, 2010; Eexpected
publication date: February 20, 201