new submission with increased dithering steps. We would like to remove the pointing manouver at the end of the second dithering pattern (between exposure 5 and 6 of orbit two, both visits) in order to get the short exposure exactly at the same pointing of the last long one. ----- Submission 1 (Fri May 13 15:28:37 GMT 2005) ----- Phase II Proposal 10552 (10552_Ph2v2p1) successfully submitted. ----- Submission 2 (Fri May 13 19:21:34 GMT 2005) ----- revised version with 3 co-Is added Assigned ID: 605 ----- Submission 1 (Sat Jan 22 00:26:57 GMT 2005) ----- Phase I Proposal 605 (Orion parallax) successfully submitted. ----- Submission 3 (Mon Jan 24 18:51:28 GMT 2005) ----- The distance of the Orion Nebula Cluster The HST Treasury program on the Orion Nebula, currently in execution, has surprisingly found that background sources are easily detected by HST at long wavelengths through selected fields within the nebula. We propose to use these background sources as a reference system to measure the trigonometric parallax of the Orion Nebula cluster. Using ACS in the F850LP filter and with a modest investment of HST time, we will reduce the error on the ~500pc distance of the Orion Nebula to ~15pc, or less, improving by a factor ~6 over current estimates. Our new value will have a major impact on star formation studies, allowing to determine with high accuracy the absolute luminosity of the cluster members and all derived stellar parameters (ages, masses, mass accretion rates...). Our current understanding of a great range of phenomena associated to the star formation activity in Orion will also benefit from an improved distance estimate.
We observe a field withing the Orion Nebula at two epochs ~6 months apart to measure the parallax of the Orion Nebula Cluster against the background stars. Each epoch corresponds to a visit of 2 consecutive orbits, where we take long and short exposures. We opted for the F814W filter, which has better PSF and field distorsion calibration than the similar F850LP. The two visits are identical and at the same target point, with aperture at the center of the ACS/WFC. The orient angles of the telescope are 40 and 248 degrees for the two visits. For our scientific goal it is important to maximize the time difference between the two visits, which should be as close as possible to 6 months. The current planning assumes 2 gyro mode. This forces us to schedule the observations around Aug 15, 2005 (ORIENT=248) and around Jan 20, 2006 (ORIENT=40deg), approximately 5 months apart. At these dates the ORIENT angles are strongly constrained and turn out to be different by more than 180deg. Thus, the corners of the ACS field are not imaged both times, reducing the number of sourcers useful to estimate the parallax. If three gyro mode becomes available either in one of both visits, we would like to replan this program to increase the time/parallactic baseline and equalize the telescope ORIENT angles. STAR FORMATION 12 false 0.0 false false false false false SUPPORTED STELLAR CLUSTER STAR FORMING REGION J2000 05 35 29.0000 -05 30 52.00 J2000 STELLAR CLUSTER STAR FORMING REGION J2000 05 35 29.0000 -05 30 52.00 J2000 ACS/WFC Imaging No No F850LP ACS/WFC Imaging No No F850LP ACS/WFC Imaging No No F850LP POS-TARG DITHER 3.2 LINE 3.2 false false 97.36 4 19.91 ACS-WFC-DITHER-BOX 1 false C:\Documents and Settings\robberto\Local Settings\Temp\OPVisit45180.xml (Tic-Visit :proposal-id 10552 :visit-id "01" :proposal-version -1 :trans-version "20050323" :date "13-May-2005 15:20:49.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 3410688 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10552 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10552 :visit-id "01" :orbit-number 1 :pcs-time 367 :si-vis-utilization 2836 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10552 :visit-id "01" :orbit-number 2 :pcs-time 367 :si-vis-utilization 2725 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) true 2 0 C:\Documents and Settings\robberto\Local Settings\Temp\OPVisit45174.xml C:\Documents and Settings\robberto\My Documents\GO10552\OP-cache\10552_Ph2revised-v02.xml (Tic-Visit :proposal-id 10552 :visit-id "02" :proposal-version -1 :trans-version "20050323" :date "13-May-2005 13:58:06.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 3410688 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10552 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10552 :visit-id "02" :orbit-number 1 :pcs-time 367 :si-vis-utilization 2836 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10552 :visit-id "02" :orbit-number 2 :pcs-time 367 :si-vis-utilization 2725 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) true 2 0 C:\Documents and Settings\robberto\Local Settings\Temp\OPVisit45177.xml