Engineering topics

Jewitt, David C.

Publications and source records attributed to Jewitt, David C..

5 records

NASA NTRS1998

Kuiper Belt Objects Along the Pluto Express Path

The science objective of this work was to identify objects in the Kuiper Belt which will, in the 5 years following Pluto encounter, be close to the flight path of NASA's Pluto-Kuiper Express. Currently, launch is scheduled for 2004 with a flight time of about 1 decade. Early identification of post-Pluto targets is important for mission design and orbit refinement. An object or objects close enough to the flight path can be visited and studied at high resolution, using only residual gas in the thrusters to affect a close encounter.

Jewitt, David C.↗

NASA NTRS1995

The solar system beyond Neptune

We present the results of a deep optical survey for distant solar system objects. An area of 1.2 sq deg of the ecliptic has been imaged to apparent red magnitude 25, resulting in the detection of seven trans-Neptunian objects. These are the first detected members of a trans-Neptunian disk that compries about 35 000 objects larger than 100 km in the 30-50 AU heliocentric distance range. We interpret the new measurements using a set of Monte Carlo models in which the effects of observational bias in the data are taken into account.

Jewitt, David C.↗

NASA NTRS1994

Submillimeter constraints on dust near Lindroos' post T Tauri stars

Young stars from the dynamical sample identified by Lindroos (A&A, 156,223 (1986)) have been observed at 800 micrometers wavelength using the James Clerk Maxwell Telescope on Mauna Kea. The new data are used to constrain the mass of circumstellar dust around these stars. The Lindroos sample is dominated by low-mass stars of age (3-150) x 10(exp 6) yr, intermediate in age between the T Tauri and main-sequence stars. When combined with previous measurements, the present observations are compatible with the depletion of circumstellar dust on a time scale tau approximately 10(exp 7.0) yr. If this dust is present in circumstellar disks, then tau represents the lifetime of these disks.

Jewitt, David C.↗

NASA NTRS1990

Cometary activity in 2060 Chiron

Results of a 2-yr (1988-90) investigation of cometary activity in 2060 Chiron based on CCD photometry and spectroscopy are reported. The photometry observations include a new rotational light curve of Chiron, a newly refined rotation period, recent developments of its long-term photometric behavior and surface brightness profiles, a deep image of the coma of Chiron, and narrowband images at wavelengths ranging from 3200 to 6840 A. The spectroscopic data include moderate resolution CCD spectra (10-20 A FWHM). Major results include the detection of impulsive brightening on a time scale of hours, evidence for a secular change in the blue portion of the reflectivity spectrum of the nucleus, no evidence for Rayleigh scattering in the near ultraviolet, and an upper limit of the column density of CO(+) ions in the coma.

Luu, Jane X.↗

NASA NTRS1990

Charge-coupled device spectra of asteroids. I - Near-earth and 3:1 resonance asteroids

Main-belt asteroids and cometary nuclei are both frequently suggested sources of the relatively short-lived near-earth asteroids (NEAs). The asteroidal origin hypothesis is studied by obtaining new high-quality reflectivity spectra of 19 NEAs and 23 asteroids near the 3:1 resonance, and by performing a systematic comparison of these two groups of spectra. Nonparametric statistical tests are used to check for consistency between the color distributions of the two populations. The tests indicate that the difference between the two distributions is generally not significant at the 3 sigma level. However, this conclusion is dependent on the (unknown) size distribution of the NEAs. The observations are compatible with the hypothesis that the NEAs are derived from the 3:1 resonance region, but do not imply that this is the only possible source region.

Luu, Jane X.↗