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NASA NTRS1974

Comet Encke flyby - Asteroid rendezvous mission

A multitarget mission mode is described which utilizes the solar electric propulsion (SEP) capability to rendezvous with an asteroid after the encounter with Encke. This mode can be defined as a 'no-risk' Encke flyby mission relative to SEP technology. Launched in mid-1980, the earth-Encke transfer is all-ballistic, and SEP operation begins after comet encounter and is relied upon only to accomplish the secondary target objectives. The discussion is based on an exploratory analysis and is therefore limited in scope to a description of trajectory profile and spacecraft mass characteristics.

Friedlander, A. L.↗

NASA NTRS1974

Infrared observations of comet Kohoutek near perihelion

Observations between 0.55 and 18 microns show that after perihelion passage, comet Kohoutek possessed an infrared tail and antitail. The coma and the tail have the silicate signature and contain 'black material' which acquires a temperature higher than the blackbody temperature at the given distance from the sun. The antitail shows the colors of a blackbody at a lower temperature, suggesting that the particles are larger than those in the coma and the tail.

Ney, E. P.↗

NASA NTRS1974

Comet Kohoutek - Ultraviolet images and spectrograms

Emissions of atomic oxygen (1304 A), atomic carbon (1657 A), and atomic hydrogen (1216 A) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on Jan. 8, 1974. Analysis of the Lyman alpha halo at 1216 A gave an atomic hydrogen production rate of 4.5 x 10 to the 29th atoms per second.

Opal, C. B.↗

NASA NTRS1974

Rocket ultraviolet spectrophotometry of Comet Kohoutek /1973f/

On January 5, 1974, the ultraviolet emissions from Comet Kohoutek (1973f) in the spectral range from 1200 to 3200 A were studied with the aid of a rocket carrying two spectrophotometers. In addition to the Lyman alpha line of atomic hydrogen at 1216 A and the (0,0) and (1,1) bands of OH at 3090 and 3142 A, both atomic oxygen (1304 A) and atomic carbon (1657 and 1561 A) were detected.

Feldman, P. D.↗

NASA NTRS1974

Comet Kohoutek observations from Skylab

The original intent of the Skylab observations of comet Kohoutek, as stated by Operation Kohoutek, was to provide (1) long-term viewing, (2) near-perihelion viewing, (3) astronaut response, and (4) payload optimization, allowing Kohoutek to be monitored in the ultraviolet and visible-light ranges regardless of its angular separation from the sun. The preliminary results made available thus far indicate that through its man-aided flexibility and broad range of capabilities Skylab was indeed able to achieve this intent.

Snoddy, W. C.↗

NASA NTRS1974

Mission design for a ballistic slow flyby Comet Encke 1980

Preliminary mission analyses for a proposed 1980 slow flyby (7-9 km/s) of comet Encke are presented. Among the topics covered are science objectives, Encke's physical activity and ephemeris accuracy, trajectory and launch-window analysis, terminal guidance, and spacecraft concepts. The nominal mission plan calls for a near-perihelion intercept with two spacecraft launched on a single launch vehicle. Both spacecraft will arrive at the same time, one passing within 500 km from Encke's nucleus on its sunward side, the other cutting through the tail region. By applying a small propulsive correction about three weeks after the encounter, it is possible to retarget both spacecraft for a second Encke intercept in 1984. The potential science return from the ballistic slow flyby is compared with other proposed mission modes for the 1980 Encke flyby mission, including the widely advocated slow flyby using solar-electric propulsion. It is shown that the ballistic slow flyby is superior in every respect.

Farquhar, R. W.↗

NASA NTRS1974

Microwave and infrared observations of molecular spectra in Comet Kohoutek

Transitions of the possible parent molecules H2O, NH3, CH3OH, and N2O as well as the OH radical were searched for in Comet Kohoutek (1973f) in the frequency range 22.2-25.2 GHz. These molecules were not detected but the upper limits for the optical depth, mean column density, and the production rate are derived for each of the molecules. These results are discussed and compared with the reported detections of HCN and CH3CN emission and OH absorption.

Townes, C. H.↗

NASA NTRS1975

Infrared spectroscopy of Comet Kohoutek

Interferometry observations from 90-in. and 61-in. telescopes tracking the Comet Kohoutek are summarized. Laboratory reflection studies of ices potentially useful for future cometary work were conducted. The frosts studied included: H2O, CO2 NH3, H2S, CH4, NH4HS, and ammonia polysulfide. The frost spectra show remarkable changes with the temperatures, particularly in the case of hydrogen sulfide. Additional analysis found the variation in the H2S ice spectrum to be due to a phase change from a low temperature tetragonal unit cube to a higher temperature face-centered cubic structure. The spectra data indicate that if frost spectra are required for comparison with observed cometary or planetary absorption, the temperature of the frost must be matched.

Fink, U.↗

NASA NTRS1974

Solar electric propulsion spacecraft power subsystem for an Encke comet rendezvous mission

This paper presents the preliminary functional description of a solar electric propulsion spacecraft power subsystem for an Encke comet rendezvous mission in the 1980s. This description has been derived from the study of the mission requirements and constraints and the study of integrating a solar electric propulsion module with an existing spacecraft. Tradeoff studies performed in the process of selecting power subsystem parameters and performance characteristics are described. The power subsystem designs draw heavily on the designs for existing spacecraft and technology being developed in the electric propulsion research and development program supported by NASA.

Costogue, E. N.↗

NASA NTRS1974

Lyman-alpha imagery of comet Kohoutek, and far-UV magnitudes of stars

The Apollo-16 S201 electronographic camera backup model was modified for use on the Skylab AMS-SAL, which reduced its 20 deg FOV to about 7 deg unvignetted. Over 500 frames were exposed by automatic sequencer through LiF and CaF2. The Lyman-alpha halo of comet Kohoutek has been analyzed for nine occasions, and its long, pointed tail was imaged in 1250-1600 A only near perihelion. Far-UV magnitudes and colors are being derived for about 200 stars, nebulae, and galaxies. Redshifted Lyman-alpha emission from intergalactic atomic hydrogen was not detected in 7 clusters of galaxies. About 25% of the exposed frames were degraded by water damage, electrical discharges, decline in photocathode sensitivity, and loss of AMS mirror reflectance.

Page, T.↗

NASA NTRS1974

Skylab observations of Comet Kohoutek

This paper summarizes the special operational procedures developed to observe the Comet Kohoutek from Skylab and the scientific results from these observations. Emphasis is placed on results from Skylab experiments S052, White Light Coronagraph; S201, Far UV Electronographic Camera; S233, Kohoutek Photometric Photography; S019, UV Stellar Astronomy; S183, Ultraviolet Panorama Telescope; and S082B, Ultraviolet Spectrography. Visual observations by the astronaut crew and the significance of these observations are discussed.

Snoddy, W. C.↗

NASA NTRS1974

The C-12/C-13 ratio in comet Kohoutek /1973f/

Results are presented for photoelectric scans of the C sub 2 1 to 0 band head at 4737 A at resolutions of 0.14 to 0.50 A in the comet Kohoutek. On the basis of medium-resolution scans and of one high-resolution scan two values are obtained for the C-12/C-13 ratio which are consistent within the experimental errors with the terrestrial values of C-12/C-13 equal to 89. The study also demonstrates the limitations imposed by NH2 blends.

Danks, A. C.↗

NASA NTRS1974

Interpretation of the anti-tail of Comet Kohoutek as a particle flow phenomenon

The appearance of a 'sunward' spike, opposite in apparent orientation to the normal Type-II tail in Comet Kohoutek is interpreted as evidence for large particles ejected near perihelion. It is shown that the shape and orientation can be satisfactorily explained in this manner, after consideration of the increased mass flow at decreasing heliocentric distance. The apparent length of the spike can be a measure of the particle size and density, and a value of about 0.004 g/sq cm for the product of particle size and density fits the Skylab observations.

Gary, G. A.↗

NASA NTRS1974

A search for H2O and CH4 in Comet Kohoutek

A spectroscopic search for H2O and CH4 in Comet Kohoutek (1973f) was made using a Pepsios interferometer. No evidence was found for either molecule, allowing to set an upper limit on their production rates (on about Jan. 21, 1974) of Q(H2O) less than 6.2 times 10 to the 28th power per sec and Q(CH4) less than 20 times 10 to the 30th power per sec.

Traub, W. A.↗

NASA NTRS1974

Molecule searches in Comet Kohoutek /1973f/ at microwave frequencies

Nine transitions of the possible parent molecules H2O, NH3, CH3OH and N2O as well as the OH radical were searched for in Comet Kohoutek (1973f) in the frequency range 22.2-25.2 GHz. These molecules were not detected, but the upper limits for the optical depth, mean column density and the production rate are derived for each of the molecules. These results are discussed and compared with the reported detections of HCN and CH3CN emission and OH absorption.

Mango, S. A.↗

NASA NTRS1974

A search for microwave emission from CH in Comet Kohoutek /1973f/

A search was conducted for the three 9-cm transitions of the ground state Lambda-doublet of CH in comet Kohoutek, using the CSIRO 64-m radio telescope and the Onsala Space Observatory's 25.6-m telescope. No lines were detected during the observing periods, and upper limits are given for the corresponding antenna temperatures.

Rydbeck, O. E. H.↗

NASA NTRS1974

An upper limit on the evolution of carbon monoxide from Comet Kohoutek

An upper limit on the rate of evolution of CO from Comet Kohoutek has been obtained from a search for resonant scattering of sunlight near 4.7 microns. The observations were made approximately two months after perihelion. The rate of evolution of CO at that time was apparently less than that of CH3CN observed before perihelion.

Wollman, E. R.↗

NASA NTRS1974

Tail structures far from the head of Comet Kohoutek. I

Two tail structures 0.1 AU from the head of Comet Kohoutek were photographed during January 1974. One was a wavy structure resembling a helix while the other was an irregular swan-like cloud. Both features were propagating down the tail at approximately 250 km/sec, and the observed speed is probably the phase speed. We discuss the physical origin of these structures and interpret the helix as a kink instability resulting from currents flowing along the tail axis.

Hyder, C. L.↗

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