Edward Wood Dunham

Size and albedo of Kuiper belt object 55636 from a stellar occultation

The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX300) is a member of the water-ice-rich Haumea KBO collisional family. The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1u2009Gyr ago. Here we report observations of a multi-chord stellar occultation by KBO 55636, which occurred on 9 October 2009 ut. We find that it has a mean radius of 143u2009±u20095u2009km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales.

FRESIP: A Mission to Determine the Character and Frequency of Extra-Solar Planets Around Solar-Like Stars

FRESIP (FRequency of Earth-Sized Inner Planets) is a mission designed to detect and characterize Earth-sizes planets around solar-like stars. The sizes of the planets are determined from the decrease in light from a star that occurs during planetary transits, while the orbital period is determined from the repeatability of the transits. Measurements of these parameters can be compared to theories that predict the spacing of planets, their distribution of size with orbital distance, and the variation of these quantities with stellar type and multiplicity. Because thousands of stars must be continually monitored to detect the transits, much information on the stars can be obtained on their rotation rates and activity cycles. Observations of p-mode oscillations also provide information on their age and composition. These goals are accomplished by continuously and simultaneously monitoring 500 solar-like stars for evidence of brightness changes caused by Earth-sized or larger planetary transits. To obtain the high precision needed to find planets as small as the Earth and Venus around solar-like stars, a wide field of view Schmidt telescope with an array of CCD detectors at its focal plane must be located outside of the Earths at mosphere. SMM (Solar Maximum Mission) observations of the low-level variability of the Sun (∼1:100,000) on the time scales of a transit (4 to 16 hours), and our laboratory measurements of the photometric precision of charge-coupled devices (1:100,000) show that the detection of planets as small as the Earth is practical. The probability for detecting transits is quite favorable for planets in inner orbits. If other planetary systems are similar to our own, then approximately 1% of those systems will show transits resulting in the discovery of 50 planetary systems in or near the habitable zone of solar-like stars.

System design of a mission to detect Earth-sized planets in the inner orbits of solar-like stars

A point design for a mission to detect Earth-sized planets in the inner orbits of solar-like stars is described. The observing technique is based upon continuously and simultaneously monitoring 5000 solar-like stars for brightness changes that would be caused by planets transiting their star. Detection of periodic transits of the same amplitude and duration provides for a robust method of discovery. The instrument would consist of a 1-m Schmidt telescope with an array of charge-coupled devices (CCDs) filling the 12° field of view. The instrument would be placed in a halo orbit about the L2 Lagrange point, where its viewing would not be obscured at any time by the Sun, Earth, or Moon.

Image stability requirement for the SOFIA telescope

The basis for the pointing stability requirement in the SOFIA telescope is described. Fundamentally, it is desirable to retain the diffraction-limited image quality of the telescope to the shortest wavelengths not dominated by shear-layer seeing effects or intrinsic optical quality of the telescope. Image motion will blur the images, and may cause loss of signal and increased noise in science instruments. The expected diffraction and seeing limited image quality contributions are discussed, an analysis of the effects of image motion on observations is given, and examples related to the specification and to currently predicted performance for the SOFIA telescope are presented.

95 Million Pixel Focal Plane for Use on the Kepler Discovery Mission

The primary goal of the upcoming Kepler Discovery mission is to search for terrestrial-sized planets around neighboring stars. To accomplish this mission, a space-based photometer is being developed that employs a 0.95-m aperture Schmidt telescope coupled to a very large Focal Plane Array (FPA) measuring 14″(L) × 14″(W) × 10″(D). The FPA is populated with 42 largeformat custom CCD-based detectors to yield approximately 95 million pixels in the 100 sq. deg. field of view of the instrument. Over the 4 year mission the FPA will continuously measure the relative intensity of approximately 100 thousand main sequence stars (14 ≤ mv ≤ 9) and will be capable of detecting relative changes in stellar flux on the order of 10–40 ppm (one-sigma) over transit periods ranging between 2 to 16 hours. All critical electronics are housed immediately behind the FPA, which yields a low-noise, compact design that is both robust and fault tolerant. The design and development of the FPA and custom CCD-based detectors is discussed along with the results from detailed performance models.

A PORTABLE TELESCOPE, PHOTOMETER, AND DATA-RECORDING SYSTEM

A description is presented of a portable telescope, two-channel photometer and high-speed data-recording system that meet the unique requirements of occultation astronomy. The instrumentation has been designed for portability, high time resolution, accurate absolute timing, and ease of use. The instrumentation includes a light-weight 35.5-cm (14-inch) objective portable telescope, a two-channel high-speed photometer and a data-recording system built into a suitcase. The equipment has been successfully used in field operations and at fixed observatories in India, Australia, and Hawaii.