The latest update on
developments concerning the Leonid MAC airborne campaigns.
Update November 24, 2001
Results of near-real time meteor flux measurements
2001 LEONID MAC MISSION A SUCCESS
The meteor storm that dazzled observers in Northern
America was studied from an altitude of 40,000 ft by a team of scientists in a
NASA sponsored "Leonid Multi-Instrument Aircraft Campaign". Onboard the NKC-135
instrumented tanker "FISTA", the researchers trained a wide array of optical and heat
sensors to the rain of meteors. After weeks of intense preparations
under very difficult circumstances by the 418th Flight Test Squadron and participating researchers,
the aircraft departed from Edwards AFB
at 5:45 UT November 18, after a brief potentially
mission-grounding loss of a walky-talky had been resolved. The flight commenced to
Alabama, where the plane turned west on a slow trajectory to cover the anticipated
storm profile. Soon, numerous bright meteors were detected, sometimes 3-4 at a
time. On several occasions, the pilots adjusted the heading
of the aircraft to help point the instruments towards sudden persistent luminous
trains. In one instance by turning the aircraft 180 degrees. Close contact with
aircraft operators prevented undue concern from the sudden and irregular aircraft
motions. A spectacular sporadic fireball marked the the end of the night. Landing
occurred around 6:30 am in morning twilight.
It is still too early to know what new data were retreived
during the mission. Researchers will spend much of the next year sorting out the
gigabytes of data. We do know that, for the first time, the mid-infrared sensor "BASS"
was successfully pointed at a persistent train. This will help clarify the role of dust
in explaining the mid-IR emission of trains detected during the 1999 Leonid MAC
mission and perhaps confirm the presence of
surviving organic molecules in the debris. BASS was operated by Dr. Ray Russell and Dr. David
Lynch of the Aerospace Corporation. Several high-resolution optical spectra were
recorded by a CCD spectrograph, operated by Emily Schaller of Darthmouth College.
These data probe the temperature and physical state in the hottest regions of the
meteor, which determine the survivability of organic molecules.
Rick Rairden of Lockheed, Palo Alto,
reported the detection of several UV spectra that may help put stronger limits on
the amount of organic breakup products in the meteor plasma. With the help of the
NASA Ames Imaging Technology branch, High-Definition TV spectra were taken for
meteor composition. Finally, slit-spectra of persistent trains were
obtained by Avi Mandell of Penn State University, which may help confirm that most
of the glow is due to emissions from the iron oxyde molecule.
flux measurements were reported from aircraft (Peter Gural, Mike Koop et al.)
and from two ground-stations. The
ground sites at Mount Lemmon Observatory, Arizona (David Holman, Jim Richardson
et al.), and at Alice Springs, Australia (Morris Jones, Jane Houston Jones et al.),
were hampered by clouds in the beginning of the night, but cleared up miraculously
during the peak of the shower. Early results show that the 1767 and 1699/1866 dust
trails dominated Leonid shower activity. The model by Brown and Cook, favoring the
1799 dust trail, was proven incorrect. Unlike models by Asher and McNaught,
the peak rates of the 1699/1866 dust trail were not a factor of ten higher than
that of the 1767 dust trail. The model by Lyytinen and Van Flandern and that of
Jenniskens are consistent with the observations. Both are expected to evolve based
on the current observations. Lyytinen also predicted the observed late peak time of
the1767-dust trail encounter based on the shape of the dust trail near Earth's orbit
causing an extended encounter.