<=== observer ===> "CGRY",\ "Gry, C.",\ "",\ "Laboratoire d'Astronomie Spatiale",\ "",\ "B.P. 8",\ "13376",\ "Marseille Cedex 12",\ "France",\ " 33 91661855",\ " 33 91055966",\ "cecile@astrsp-mrs.fr" <=== proposal ===> "ISM_IIA",1,2,\ {"diffuse interstellar medium","molecular clouds","dust properties"},\ {"LWS consortium","A. Leger","H. Walker"} <=== title ===> STUDY OF THE LOW DENSITY COMPONENTS OF THE ISM THE INTERSTELLAR CIRRUS <=== abstract ===> SCIENTIFIC ABSTRACT The ISO LWS gives the opportunity to perform IR spectroscopic observations of extended, weak sources like the cirrus, evidenced by IRAS at high galactic latitude. It allows to study gas properties through fine structure emission lines and to correlate these emission with the dust spectrum observed simultaneously. In particular the [CII] 158 um line is believed to be the more effective coolant for the considered diffuse regions so these observations should give information on the role of dust and small particles in the heating of the gas. OBSERVATION SUMMARY We will observe a small number of diffuse clouds, with several positions presenting different characteristics within the cloud (transition regions from atomic to molecular gas or regions presenting IR colour spatial variations). The [CII] 158 um line is expected to be the dominant emission line. Following the UV-absorption derived C+ cooling rate (Gry et al., 1992, A&A 266, 457) and the estimation of the FIR emission (Boulanger and Perault, 1988, ApJ 330, 964) we expect a contrast between the [CII] line and the adjacent continuum around 4. A recent analysis of the COBE data (Benett et al., 1993, COBE preprint) finds this contrast to be only 1 in the Galactic plane and 0.5 at b=50. However these values show that grating spectra should be sufficient for accurate [CII] line measurements. Other lines could be of interest in the LWS range, like [OI] 63.18 um, [OI] 145.53 um, [OIII] 51.82 um, [OIII] 88.36 um, [FeII] 51.30 um, [FeII] 87.38 um, [NII] 121.89 um, [FeIII] 51.7 um, [FeIII] 105.4 um and [NIII] 57.33 um. However they are expected to be much weaker than the [CII] line and their detection could only be marginal. The strategy will thus be to take a full grating spectrum for each position. The exposure times are calculated with AOT LWS01 (full grating scan) with 2 samples per resolution element, on the basis of a S/N around 10 for the continuum at 100 um. They should unfortunately only give a S/N of the order of 3 at 60 um for our objects, but a confortable S/N of 15 at 158 um. The IRAS fluxes considered have previously been corrected for the revised calibration of IRAS fluxes with COBE data. Off-source positions are required for extracting the background emission. For each object, we will observe one position close to the cloud, with the longest exposure time used for the object. <=== scientific_justification ===> SOURCE LIST -------------------------------------------------------------------------------- Object RA dec F100mu F60 Texp Telt S/N S/N 1950 Jy Jy min sec at100mu at60mu -------------------------------------------------------------------------------- Ursa Major Pos 1 093458.6 +703142 0.7 0.19 83 25 10 1.9 Pos 2 093013.1 +703219 0.33 0.13 83 25 5 1.3 Pos 3 092437.8 +704407 1.0 0.21 49 14 11 1.6 Pos 4 094105.6 +703715 0.67 0.11 83 25 10 1.3 ref 1 091709.5 +704029 83 25 -------------------------------------------------------------------------------- Cham G300-15 Pos 1 114948.1 -785251 1.03 0.40 49 14 10 3.0 Pos 2 114610.0 -790119 1.39 0.57 37 10 13 3.8 Pos 3 115308.7 -790412 2.37 0.73 19 4 15 3.0 Pos 4 115200.0 -791500 1.0 49 14 10 ref 1 114406.6 -782953 49 -------------------------------------------------------------------------------- L1780 Pos 1 153820.6 -070500 0.66 0.29 60 18 8 2.5 Pos 3 153800.4 -070000 1.73 0.72 31 8 14 4.1 Pos 4 153651.9 -070230 2.38 0.61 19 4 15 2.7 Pos 7 153633.8 -070200 1.47 0.40 31 8 12 2.3 ref 1 153521.3 -065029 60 -------------------------------------------------------------------------------- L1642 Pos 1 043437.4 -151029 0.67 0.25 86 28 10 2.7 Pos 2 043326.9 -144530 1.54 0.35 37 10 15 2.3 ref 2 042924.2 -132525 86 -------------------------------------------------------------------------------- SPACECRAFT TIME DISTRIBUTION Time distribution for autumn launch targets: Team top 40% second 30% last 30% LWS: 22578 sec 15502 sec 9670 sec Time distribution for spring launch targets: Team top 40% second 30% last 30% LWS: 22418 sec 13278 sec 13196 sec <=== autumn_launch_targets ===> 1, "LWS01",1.0,"N","Ursa Major #1 ",09.58294,+70.52833,1950,0.,0.,5174, 0 2, "LWS01",2.0,"N","Ursa Major #2 ",09.50364,+70.53861,1950,0.,0.,5174, 0 3, "LWS01",1.0,"N","Ursa Major #3 ",09.41050,+70.73528,1950,0.,0.,3104, 0 4, "LWS01",1.0,"N","Ursa Major Ref#1",09.28597,+70.67472,1950,0.,0.,5174, 0 5, "LWS01",1.0,"N","Cham G300-15 #1 ",11.83003,-78.88083,1950,0.,0.,2748, 6 6, "LWS01",1.0,"N","Cham G300-15 #2 ",11.76944,-79.02194,1950,0.,0.,2254, 7 7, "LWS01",1.0,"N","Cham G300-15 #3 ",11.88575,-79.07000,1950,0.,0.,1180, 8 8, "LWS01",1.0,"N","Cham Ref #1 ",11.73517,-78.49806,1950,0.,0.,2944, 0 9, "LWS01",3.0,"N","L1780 #1 ",15.63906,-07.08333,1950,0.,0.,3320,10 10,"LWS01",3.0,"N","L1780 #4 ",15.61442,-07.04167,1950,0.,0.,1180, 0 11,"LWS01",3.0,"N","L1780 #7 ",15.60939,-07.03333,1950,0.,0.,2050,12 12,"LWS01",3.0,"N","L1780 Ref #1 ",15.58925,-06.84139,1950,0.,0.,3140, 0 13,"LWS01",2.0,"N","Ursa Major #4 ",09.68489,+70.62083,1950,0.,0.,5174, 0 14,"LWS01",2.0,"N","Cham G300-15 #4 ",11.86667,-79.25000,1950,0.,0.,3104, 0 15,"LWS01",2.0,"N","L1780 #3 ",15.63344,-07.00000,1950,0.,0.,2050, 0 <=== spring_launch_targets ===> 1, "LWS01",1.0,"N","Ursa Major #1 ",09.58294,+70.52833,1950,0.,0.,5174, 3 2, "LWS01",2.0,"N","Ursa Major #2 ",09.50364,+70.53861,1950,0.,0.,5174,12 3, "LWS01",1.0,"N","Ursa Major #3 ",09.41050,+70.73528,1950,0.,0.,3104, 4 4, "LWS01",1.0,"N","Ursa Major Ref#1",09.28597,+70.67472,1950,0.,0.,5014, 0 5, "LWS01",1.0,"N","Cham G300-15 #1 ",11.83003,-78.88083,1950,0.,0.,2748, 6 6, "LWS01",1.0,"N","Cham G300-15 #2 ",11.76944,-79.02194,1950,0.,0.,2254, 7 7, "LWS01",1.0,"N","Cham G300-15 #3 ",11.88575,-79.07000,1950,0.,0.,1180, 8 8, "LWS01",1.0,"N","Cham Ref #1 ",11.73517,-78.49806,1950,0.,0.,2944, 0 9, "LWS01",3.0,"N","L1642 #1 ",04.57706,-15.17472,1950,0.,0.,5304,10 10,"LWS01",3.0,"N","L1642 #2 ",04.55747,-14.75833,1950,0.,0.,2588, 0 11,"LWS01",3.0,"N","L1642 Ref #2 ",04.49006,-13.42361,1950,0.,0.,5304, 0 12,"LWS01",2.0,"N","Ursa Major #4 ",09.68489,+70.62083,1950,0.,0.,5000, 0 13,"LWS01",2.0,"N","Cham G300-15 #4 ",11.86667,-79.25000,1950,0.,0.,3104, 0