The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU69's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

By A. B. SCHULTZ1, R. G. LYON1, I. JORDAN2, M. KOCHTE3, F. BRUHWEILER4, M. RODRIGUE5, D. BENNUM5, P. CHEN6, D. GEZARI1, D. FRAQUELLI2, AND K. -P. CHENG7 NASA/Goddard Space Flight Center, Greenbelt, MD 20771 Computer Sciences Corporation and The Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 Computer Sciences Corporation and The John Hopkins University, 3400 N. Charles Street, Baltimore MD 21218 Department of Physics, Catholic University of America, Washington, DC 20064 Department of Physics, University of Nevada, Reno, NV 89557 Catholic University of America and NASA/Goddard Space Flight Center, Greenbelt, MD 20771 Department of Physics, California State University Fullerton, Fullerton, CA 92634

We derive improved system parameters for the HD 209458 system using a model that simultaneously fits both photometric transit and radial velocity observations. The photometry consists of previous Hubble Space Telescope STIS and FGS observations, 12 I-band transits observed between 2001 and 2003 with the Mount Laguna Observatory 1 m telescope, and six Strömgren b + y transits observed between 2001 and 2004 with two of the Automatic Photometric Telescopes at Fairborn Observatory. The radial velocities were derived from Keck HIRES observations. The model properly treats the orbital dynamics of the system and thus yields robust and physically self-consistent solutions. Our set of system parameters agrees with previously published results, although with improved accuracy. For example, applying robust limits on the stellar mass of 0.93-1.20 M☉, we find 1.26RJ < Rplanet < 1.42RJ and 0.59MJ < Mplanet < 0.70MJ. We can reduce the uncertainty of these estimates by including a stellar mass-radius relation constraint, yielding Rplanet = RJ and Mplanet = MJ. Our results verify that the planetary radius is 10%-20% larger than predicted by irradiated planet evolution models, confirming the need for an additional mechanism to slow the evolutionary contraction of the planet. A revised ephemeris is derived, T0 = 2,452,854.82545 + 3.52474554E (HJD), which now contains an uncertainty in the period of 0.016 s and should facilitate future searches for planetary satellites and other bodies in the HD 209458 system.

This paper will discuss the system and mission requirements needed for a planet-finding mission consisting of two spacecraft -a space telescope platform and an external occulter vehicle.This two-vehicle configuration may be operated with only modest enhancements to existing space operations systems.These requirements will encompass conventional, new, and unique spacecraft operations domains.Topics this paper will explore include inter-spacecraft operations and science and mission support.

We report work in progress on a self consistent dynamical model of the transiting extrasolar planet system HD 209458. We are attempting to simultaneously model the photometric eclipses and spectroscopic radial velocity observations. We have obtained a good fit to the light curves and radial velocity curve, and in particular, the "Rossiter effect" distortion of the radial velocities during transit is reproduced.

We present optical simulations of a new approach to directly image terrestrial planets. Terrestrial planets typically are 10 orders of magnitude fainter than the central star, a difficult challenge for any optical system. Our studies show that the combination of an external occulter and an apodizer yields the required contrast, with significantly reduced requirements on stray light and diffraction. This mitigates the very high mirror tolerances required of other coronagraphic methods and makes exo-planet detection feasible with current technology.

We present preliminary analysis of new HST observations of the transiting extrasolar planet HD 209458b. Photometric observations were obtained with the Fine Guidance Sensor (FGS) on the Hubble Space Telescope (HST), providing milli-mag precision and high time resolution (40 Hz). The FGS photometry allows us to derive precise stellar/orbital parameters (ephemeris, inclination, limb darkening) and planetary radius, and also allows a search for the presence of planetary rings and satellites. We discuss preliminary results and two approaches to modelling the observations.

We derive a substantially improved ephemeris for HD 209458b based on photometric transit observations. I-band observations taken at SDSU's Mount Laguna Observatory during the 2001, 2002, and 2003 observing seasons were combined with transit observations by the Hubble Space Telescope STIS (Brown et al. 2001) and FGS (Schultz et al. 2003), and additional ground-based APT photometry. The Eclipsing Light Curve code (ELC) for binary star modelling was used to fit the observations. We derive an orbital period of P 3.52474541 +/- 0.00000025 days and mid transit time of T-0 = 2452854.825415 +/- 0.000060 HJD. The uncertainty in period is only 0.021 seconds, over 15 times more precise than previous results.

We present the data, and modeling and analysis results from the photometric monitoring of five planetary transits of HD 209458 using the Fine Guidance Sensors (FGS) onboard the Hubble Space Telescope (HST). We have now included the output from all four FGS photometers in our data reduction and analysis increasing our S/N over our previous results. We have modeled the transits as an opaque spherical planet in a circular orbit about a limb darkened spherical star and simultaneously fit the model to the FGS data and published STIS transit data. The measured light curves show small features, a fraction of the transit depth. Some of these faint bumps and ripples appear to be real. We present an analysis of the FGS transit light curves, showing the results of the model fitting and a search for a possible planetary satellite.

The standard approach to achieving TPF-level starlight suppression has been to couple a few techniques together. Deployment of a low- or medium-performance external occulter as the first stage of starlight suppression reduces manufacturing challenges, mitigates under-performance risks, lowers development costs, and hastens launch date for TPF. This paper describes the important aspects of a conceptual 4-metre apodized square aperture telescope system utilizing a low-performance external occulter. Adding an external occulter to such a standard TPF design provides a benefit that no other technique offers: scattered and diffracted on-axis starlight is suppressed by orders of magnitude before reaching the telescope. This translates directly into relaxed requirements on the remainder of the optical system.

Free-flying external coronagraphs for space telescopes have been studied many times since the 1960s, but few schemes have been generally viewed as yielding a mission with an acceptable cost. Results of a design study are presented on modification of the Nexus L2 mission to perform as an occulter for NGST. Such a mission would have a much smaller cost than previous occulter ideas. A suitably configured spacecraft, incurring only a small percentage mass increase, can be transformed into a free flying occulter capable of performing unique science in conjunction with a space telescope. The 'mission extension' concept serves as an example applicable to other mission.

We describe a 1-meter space telescope plus free-flying occulter craft mission that would provide direct imaging and spectroscopic observations of Jovian and Uranus-sized planets about nearby stars not detectable by Doppler techniques. The Doppler technique is most sensitive for the detection of massive, close-in extrasolar planets while the use of a free-flying occulter would make it possible to image and study stellar systems with planets comparable to our own Solar System. Such a mission with a larger telescope has the potential to detect earth-like planets.Previous studies of free-flying occulters reported advantages in having the occulting spot outside the telescope compared to a classical coronagraph onboard a space telescope. Using an external occulter means light scatter within the telescope is reduced due to fewer internal obstructions and less light entering the telescope and the polishing tolerances of the primary mirror and the supporting optics can be less stringent, thereby providing higher contrast and fainter detection limits. In this concept, the occulting spot is positioned over the star by translating the occulter craft, at distances of 1,000 to 15,000 km from the telescope. Any source within the telescope field-of-view can be occulted without moving the telescope.In this paper, we present our current concept for a 1-m space telescope matched to a free-flying occulter, the Umbral Missions Blocking Radiating Astronomical Sources (UMBRAS) space mission. An UMBRAS space mission consists of a Solar Powered Ion Driven Eclipsing Rover (SPIDER) occulter craft and a matched (apodized) telescope. The occulter spacecraft would be semi-autonomous, with its own propulsion systems, internal power (solar cells), communications, and navigation capability. Spacecraft rendezvous and formation flying would be achieved with the aid of telescope imaging, RF or laser ranging, celestial navigation inputs, and formation control algorithms.

Portions of four planetary transits of HD 209458 were observed using the Fine Guidance Sensors (FGS) onboard the Hubble Space Telescope (HST). The combined data were fit with a transit model, yielding a determination of the stellar radius R∗ = 1.17± 0.03 R⊙, the planetary radius Rp = 1.43± 0.04 RJ , and the orbital inclination i= 86.1 o ± 0.1.

Free-flying external coronagraphs for space telescopes have been studied since the 1960s, but cost/ benefit analysis has not proved convincing for skeptics. A single space vehicle carrying an occulting screen can increase the contrast between a star and its orbiting extrasolar planets for a suitably designed space telescope. However, a number of advantages ensue when replacing the single occulter with a fleet of lighter-mass occulters. Target observation rates can increase in proportion to the number of coronagraphic free flying vehicles devoted to a mission. At the same time, mass requirements for individual vehicles is dramatically reduced. Mission lifetimes can at the same time potentially increase, and the risk of independent catastrophic failures onboard an occulting vehicle eliminating all science productivity for the mission are effectively vanish. Perunit vehicle costs are substantially lower than for production of a single unique craft.