ISO: Notes

Observations affected by the LWS wheel problem.

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In the course of November last year, a problem was discovered with the positioning of the LWS interchange wheel. Following this, LWS operations were suspended, as a precautionary measure. The problem has been solved and as of 31 January of this year LWS operations were fully resumed.

The LWS instrument team has examined the potential impact on all observations and determined during which observations the wheel was not positioned correctly. There are three different cases that can be distinguished:

1. Observations with the grating, during which the wheel was only slightly misplaced (less than 7 degrees). In this case there is no effect on the observation.
2. Observations with the grating, during which the wheel was significantly misplaced (more than 7 degrees). In this case there is some vignetting of the LWS beam due to the wheel misplacement. The impact is, at this stage, not considered so significant that the observation would qualify for rescheduling.
3. Observations with the FP, during which the wheel was misplaced. Since the FPs were calibrated with the wheel in the correct position, any misplacement of the wheel will put an uncalibrated part of the FP etalon meshes in the beam. Therefore any observation in this category has been recommended for rescheduling by the Project Scientist.

The tables below give the observations falling in categories 2 and 3. Table 1 lists the observations (TDT, Observer ID, Proposal ID, AOT and Target) for all observations in category 2, together with the amount of obscuration due to vignetting that was calculated for this observation. Table 2 lists all the observations in category 3 (TDT, Observer ID, Proposal ID, AOT and Target) that have been recommended for rescheduling.

Table 1. Grating observations with the wheel misplaced.
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TDT	   ObsID      PropID     AOT     Target		  Obscuration (%)
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30800602   VBUJARRA   PPNA       L02     R Sct            7
30800603   VBUJARRA   PPNA       L02     R Sct            7
30800938   KERIKSSO   PROP_394   L02     V Aql            7
32301004   SCOLGAN    NARROWLN   L02     G36.3+0.7        3
32301005   SCOLGAN    NARROWLN   L02     OFFG36.3         3
32301108   DENGELS    JUNGEPPN   L01     OH 37.1-0.8 OFF  3
32301404   MVOGEL     SYMBPHYS   L01     PU Vul           3
32301405   MVOGEL     SYMBPHYS   L01     PU Vul BG        3
35400552   HSMITH     GALXISM    L02     NGC 5195         6
35400708   JSTUTZKI   PDRDENS    L01     S106             7
35501620   VBUJARRA   PPNA       L02     M1-92            11
35501621   VBUJARRA   PPNA       L02     M1-92 OFF        11
37600944   GVDSTEEN   CNO_ABUN   L01     NGC 6891         1
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Table 2. FP observations that have been recommended for rescheduling.
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TDT	   ObsID      PropID     AOT     Target		  
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32301236   JCERNICH   CERNI_1    L04     W51 IRS2
32301237   JCERNICH   CERNI_1    L04     W51 IRS2
33101903   ABAUDRY    PROP_OH1   L04     G10.6-0.4
35102433   JCERNICH   CERNI_3    L04     NGC7027
35201408   EVDISHOE   MOLSPEC    L04     GL 2591 NIRS01
35400703   JSTUTZKI   PDRDENS    L04     S106
35500318   EVDISHOE   MOLSPEC    L04     DR21 FIR1
35501622   VBUJARRA   PPNA       L04     M1-92
36303850   VBUJARRA   PPNA       L04     IRAS19500-17
36303851   VBUJARRA   PPNA       L04     IRAS19500-17OFF
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ISO Science Operations
and
LWS Instrument Team
02/04/97

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