Live From...the Stratosphere
KAO Highlights for 1994


(This text was originally written by Allan Meyer and Terry Duncan on 03-April-95)

Cold water vapor detected in molecular clouds
New infrared camera images Orion nebula
Hidden supernova revealed in M 82
Coma of distant comet explored
IR spectra captured of comet hitting Jupiter

February

The first flights for the new instrument KWIC (Kuiper Widefield Infrared Camera) produced excellent diffrac-tion-limited far-infrared (37 µm) images of M 42. Developed by Gordon Stacey at Cornell University, KWIC uses a SIRTF-funded 128x128 BIB array and two Fabry-Perot etalons to provide spectral resolution in the image of up to 4000. The development of far-infrared detector arrays has greatly improved the efficiency of airborne astronomy research.

Jonas Zmuidzinas (CalTech) and his colleagues used his submillimeter spectrometer to detect cold water vapor in interstellar molecular clouds. The observed feature was a ground state transition of isotopic water, ortho-H218O, at 547GHz (0.55mm.), which was seen in absorption in SgrB2 (near the galactic center), and was seen in emission in OMC-1 (M 42) during the February flights.

March

The KAO commenced a southern hemisphere deployment to Brazil and New Zealand. Brasilia, Brazil was the base of operations for an attempt to obtain new clues to the nature of Chiron, an unusually large comet in an elliptical orbit (P=51yrs, e=0.38) between those of Jupiter and Uranus. It had been predicted that Chiron would occult a faint anonymous star, and this rare event would be visible in Brazil, the south Atlantic, and South Africa. The focal-plane instruments installed for this event included a high-speed CCD optical photometer from NASA Ames, and LIRCII (Lick Observatory Infrared Camera II), a near-infrared imaging array used to obtain K-band photometry. The PI team for these two instruments included members from Lowell Observatory, NASA Ames, Lick Observatory and the Brazilian National Observatory.

While the KAO cruised high above Brazil's tropical thunderstorms, the PI team successfully recorded several dimmings of the background star apparently due to dust and gas jets near Chiron's surface. It was later deter-mined that the KAO missed the center of Chiron's "shadow" by only 60±10 miles, setting an upper limit on the radius of the object (see Nature, vol.353, p.46 - January 5, 1995).

May

At the end of the southern hemisphere deployment, the Lick Observatory PI team used the KAO to search for an infrared emission line due to ionized nickel in other galaxies. This would be like a "smoking gun" revealing recent supernova explosions in those galaxies. Using narrow-band imaging, the Ni II (6.63 µm) line was detected in the starburst galaxy M82 during a long observing leg from Hawaii back to NASA Ames. The feature was later confirmed by spectra obtained with HIFOGS.

July

Immediately after the Airborne Astronomy symposium at NASA Ames, the KAO departed Ames for Melbourne, Australia, to get into position for the SL9 Jupiter impacts. It had been established that Jupiter could be observed longer after each impact if the KAO were based in the southern hemisphere. The visibility of the 21 predicted impacts was distributed randomly in earth longitude, but a "cluster" of 6 or 7 would occur when Jupiter was high in Australia's sky.

Three flights were flown on consecutive nights with the Cornell University instrument KEGS (Kuiper Echelle Grating Spectrometer) installed; the PI team included G. Bjoraker of GSFC, and the Cornell U. instrument team: T. Herter, G. Gull, B. Pirger and S. Stolovy. Spectra were taken with a resolution of 9000 alternately at 7.7µm and at 23µm. The 5 arc-second wide slit was centered on the impact site. As shown in the adjacent sequence, the continuum and the methane features became very bright as soon as Jupiter's rotation brought the impact site into view, and then faded with a half-hour time scale. Three high-temperature water vapor emission lines also appeared for about 10 minutes, fading away completely after 20 minutes.

On July 20 the HIFOGS (High-efficiency Infrared Faint Object Grating Spectrometer) was installed onto the KAO telescope. The P.I. instrument team was F. Witteborn, D. Wooden and R. Kozlowski (Ames); and the Guest Investigators were A. Sprague and D. Hunten (LPL). HIFOGS was used to observe the effects of the impact of fragment R on July 21, and fragments V and W the next day. Numerous spectra were obtained during the hours following each impact, spanning 4.9 - 9.4 µm (see examples in figure), and also 9.3 - 14.5 µm. Bright emission features that appeared in the post-impact spectra included water vapor (6.6 µm), methane (7.7 µm), and acetylene (13.7 µm). Line ratios indicate the water vapor was at about 500 K. Further analysis by the Guest Investigators identified an emission feature due to SO2. Sulfur dioxide is not normally present in Jupiter's atmosphere, but was apparently produced by the mixing of large quantities (~106 kg) of water vapor and sulfur in the impact area.

The FOSTER Program was represented on the Jupiter/SL9 expedition by Michael Ahern, who participated in several of the flights. In addition, the Can-Do Project, a special science education program of the Charleston County, South Carolina School District*, arranged to install a film camera on the telescope headring. The motorized camera was operated in flight by participating teachers, including Jim Nicholson, Tom O'Brien, Jeri Calhoun, Robin Ruthorford, Carol Swan, and Carol Temple.

* see National Geographic, vol. 186, no. 4, p. 54 (August 1994)

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