of 9P/Tempel 1, the Deep Impact target, from CAHA
L.M. Lara (IAA-CSIC, Spain), H. Boehnhardt (MPS, Germany), R. Gredel (CAHA, Spain), P.J. Gutiérrez (IAA-CSIC, Spain), J.L. Ortiz (IAA-CSIC, Spain), R. Rodrigo (IAA-CSIC, Spain) & M.J. Vidal-Nuñez (IAA-CSIC, Spain)
Telescope: 2.2 m at Calar Alto Observatory (CSIC-MPG) [Code 493]
Coordinates: 2°32'44.9''W, 37°13'24.5''N, 2172.62 m
Instruments: CAFOS - R and I Johnson filters, medium-resolution spectrophotometry with grism B200- and BUSCA
In January 2005 NASA's Deep
Impact (DI) spacecraft was launched to perform a cratering
experiment at Comet 9P/Tempel 1 on
Comet 9P/Tempel 1, the target
of the Deep Impact Mission, was intensively monitored from the 2.2 m telescope
at Calar Alto Observatory (MPG-CSIC) since Jan. 2005
Most of the analysis is still going on and here we only show some of the acquired images with no conclusions as every individual result must be analysed in the frame of the whole experiment results.
The complete set of images to be
shown are acquired in R Johnson with CAFOS, N is up E to the left, FOV is 5'x5'
for the frame containing the comet image as seen by the
53”x53” for the
Beside the increase of
activity as the comet approached the Sun, the most outstanding results come
from the morphological follow up of the dust structures existing in the coma
since the beginning of the monitoring, i.e. January 2005. These structures are
hidden in the nearly isotropic coma and they can be enhanced by simply applying
In January and early February, the only morphological structure noticed in the coma is a short straight feature at position angle (PA) ~250º, i.e. more than 60º out off the direction of the dust tail. The Sun position is indicated by a yellow circle.
From mid Feb., the structure in the southwest coma quadrant can be resolved into a coma fan. In early March, further straight (or slightly curved) features appear in the southern coma hemisphere and in April the coma resembled very much a porcupine pattern (similar to C/1995 O1 Hale Bopp) with features identified in PA ranging from 110º to 300º.
During May and June, the porcupine pattern is reduced to 4 straight jets. On June 14, observations from Calar Alto were the first ones in detecting an outburst of the comet, that was later on also detected by the Hubble Space Telescope and by the imaging system on the Deep Impact spacecraft. This outburst is manifested as an expanding arclet of material spanning about 120º in the NW direction.
Four days later, when the comet was successfully imaged again, this ejection of material was not seen anymore. Typical dust velocities, projected on the plane of the sky, of 50-100 m/s, produce an expansion and dilution of the shell into space.
observations were carried out "in situ" and the comet was regularly imaged in B,V,R,I Johnson. Spectrophotometric
observations were also acquired to monitor the CN, C2, C3, NH2, CH, etc.
production rates pre-impact, hours after the impact and days after the impact
where beside the skylines, gas emissions as CN, C3, C2 (Dn=0,-1) and solar light scattered by the dust particles
in the coma can be seen. This particular
spectrum was acquired on May 11, when the comet was 1.601 AU from the Sun and
0.716 AU from the Earth (still in the pre-perihelion branch). Spectra taken
during the impact phase show the same pattern although the gas emissions are
stronger and the dust ones show a remarkably asymmetry in the North-South
direction, where the slit was positioned.
Spectra taken during the impact phase show the same pattern although the gas emissions are stronger and the dust ones show a remarkably asymmetry in the North-South direction, where the slit was positioned.
From July 1st to the 3rd, the comet did not show any noticeable differences from previous weeks and months. On July 04, at 5:52UT, it was impacted by the projectile that the Deep Impact spacecraft released 24 hours before. This event was not visible from Calar Alto (it occurred during daytime). However, 16.5 hours later, when the comet became visible to CA telescopes again, the coma –before doing any processing to enhance previously existing or new structures- did show an outstanding asymmetry. After laplace filtering, the cloud of dust produced by the impact became clear and its width and expansion velocity could be determined.
A few days later, this dust cloud moving at a velocity of 100-300 m/s had expanded and diluted in such a way that it was not clearly detected in our frames anymore.
All of the data acquired during this 6 and a half months are already reduced and partially analysed. For the pre-impact phase, a paper has been submitted for publication to A&A. The impact and post-impact phase data, further results and analysis will be presented in the Asteroids, Comets and Meteors 2005 Conference,. They will be also submitted for several publications dealing with dust and gas coma: its morphology, production rates and implications on the comet nuclei derived from the Deep Impact experiment.
Although the comet has been exhaustively studied from the 1st to the 7th of July from most observatories on ground, data acquired at Calar Alto Observatory are unique in the sense that they cover more than 6 months of thorough study of the comet. The comprehension of the impact experiment itself, the short and long term effects this might have produced on the nucleus and a better understanding of the structure and composition of the comet nuclei require to have the most complete picture of the pre-impact state. The most updated baseline for pre- post- impact comparison of the comet state has been acquired from Calar Alto Observatory, and it is already having a great repercussion within the Deep Impact Project.