DAWN-FC
DAWN - Framing Camera
Dawn FC DC038 Report
Geometrical cross-calibration between FC2 and VIR
DA-FC-MPAE-RP-290 / 1-
Issue: 1
Revision: -
31/May/2010
Prepared by:
P. Gutiérrez-Marqués
T. Maue
S. Schröder
Approval Sheet
Prepared by: P. Gutierrez-Marques (signature/date)
Approved by: A. Nathues (signature/date)
Document Change Record
Iss./Rev. Date Pages affected Description D/- 31/5/2010 All first version D/a 10/06/2010 All Editorial mistakes Updated reference documents Rewording of the conclusions 1/- 10/06/2010 All Notation as first official release
Distribution Record
Holder Issue/Revision D 1 2 Configuration File (Doc) MPAe IB B�ttner UC Christensen PGM Guti�rrez-M. TM Maue C AN Nathues A A MLR Richards C C SSc Schr�der C C HSI Sierks C C ISZ Szemerey DLR Carsenty DLR Jaumann C DLR Michaelis DLR Mottola IDA Fiethe IDA Michalik JPL Raymond C JPL Polanskey C Legend: A - Approval C - Copy U - Updated Pages
Table of contents
1 General aspects .........................................................1 1.1 Scope ...............................................................1 1.2 Introduction ........................................................1 1.3 Applicable Documents ................................................1 1.4 Reference Documents .................................................1 2 Description of the activities ...........................................1 2.1 Overview ............................................................1 2.2 Geometrical cross-calibration .......................................2 3 Health status assessment ................................................2 4 Image analysis ..........................................................2 4.1 Exposure times ......................................................2 4.2 Dark current ........................................................2 4.3 Canopus positions ...................................................3 5 Conclusions .............................................................5
List of Figures
Figure 1: Comparison of FC2 dark current with previous measurements. .......3 Figure 2: Canopus position in the CCD frame during DC038 ...................3 Figure 3: Canopus position in in the CCDE frame during DC034 ...............4
List of Tables
Table 1: Canopus position in the CCD frame during DC034 and DC038 (in pixels) ................................. 4
This document contains the results of the analysis of the data acquired by the Framing Camera 2 during the DC038 operational slot. The scope of the activities was exclusively engineering, so no associated science report will be released.
This report is structured in several parts.
Section 2 describes the planned operations, including the different activities and a brief description of each.
Given that this was a re-run of a former activity, all sequences were merged into the background sequence, so no activity log is provided.
Section 3 reports on the general health status of the cameras.
Section 4 explains the evolution of the detector since launch and analyses its change in performance.
The conclusions are covered in section 5.
no. document name document number, Iss./Rev. AD1 DC038 Walkthrough DC038_Walkthrough_r2.ppt, 2/-
no. document name document number, Iss./Rev. RD1 Dawn FC DC034 Report DA-FC-MPAE-RP-285, 1/- RD2 DC018 Report DA-FC-MPAE-RP-286, 1/- RD3 DC014 Report DA-FC-MPAE-RP-287, 1/- RD4 Framing Camera ICO Report DA-FC-MPAE-RP-268, D/c
The operations of the Framing Cameras within the frame of DC038 were planned to be conducted between May 2nd 2010 (DOY 122) and May 3rd (DOY 123). There was only one major activity:
o Geometrical cross-calibration between FC2 and VIR
All the FC sequences were merged into the background sequence, so no tele-command slots were scheduled.
This activity is a re-run of DC034. It was developed to provide the co-alignment between the VIR instrument and the Framing Camera (FC2) by acquiring data with both instruments simultaneously. It consists of five concurrent observations of the star Canopus (Alpha Carinae, Vmag = -0.72) and was initiated and outlined by the VIR team.
The first 10-minute observation shows Canopus in the center of the FOV of both instruments with the FC acquiring a clear filter image at the beginning, in the middle, and at the end, followed by two OpNav images. The second observation shows Canopus in the upper left corner of the FC FOV. One clear filter image was acquired at the beginning, one after 5 minutes and one after 10 minutes. During the third observation the FC acquired 3 clear filter images with Canopus in the lower right corner of the FOV. In the fourth observation Canopus shows up again in the center of three images. During the final observation the spacecraft performed a slow slew that made Canopus appear to move through the FOV from bottom to top on twelve consecutive images.
The total number of FC images acquired with the door open was 26. Among these were 24 cross-calibration images (125 ms exposure time) and 2 windowed OpNav images (500 ms exposure time). All of them were acquired in the clear filter F1.
During the operational slot the camera performed nominal from the engineering point of view.
All the images were acquired as scheduled and received without any missing packet.
The images acquired during the operational slot were analyzed in three aspects. First, we assessed whether the exposure times were adequate. Second, the dark current was determined to monitor its long term evolution. Finally, the position of the reference star Canopus throughout the observation run was calculated for comparison with the acquisitions made by VIR.
The updated exposure values worked better than the DC034 values; no image of Canopus was overexposed, except for the two OpNav images.
The dark current generation rate was analyzed and compared with previous measurements, including some on ground. The bulk dark current, shown on Figure 1, is consistent with that determined during ICO/MGA (dotted line).
Figure 1: Comparison of FC2 dark current with previous measurements.
The position of the star was calculated by fitting a 2D Gaussian to the stellar brightness profile for each of the 26 images acquired during the activity. The positions are numbered 0 to 25 indicating the sequence in which they were acquired. 0 to 4 are centered in Canopus, 5 to 7 on the upper left quadrant; 8 to 10 in the lower right, 11 to 13 close to the center and 14 to 25 were acquired during the slow slew. Figure 2 depicts the position of Canopus for each image in DC038.
Figure 2: Canopus position in the CCD frame during DC038
Correspondingly, Figure 3 displays the position of the star during DC034. It is remarkable that, while the pattern is obviously the same for both runs, DC034 shows a poorer alignment with the s/c Y axis. This is due to the fact that the pointing commands were not updated for DC034 from the originally planned DC033.
Figure 3: Canopus position in in the CCD frame during DC034
Table 1 shows the value of the calculated positions of Canopus both for DC034 and DC038.
Table 1: Canopus position in the CCD frame during DC034 and DC038 (in pixels)
Img # DC034 X DC034 Y DC038 X DC038 Y 0 510.451 509.143 508.936 510.767 1 509.231 509.777 511.565 510.801 2 509.934 509.878 510.935 510.836 3 510.037 510.142 509.188 510.707 4 510.389 510.055 510.929 510.911 5 234.973 771.372 240.134 778.978 6 236.017 770.362 240.516 778.197 7 234.594 770.631 241.163 778.308 8 781.964 246.225 778.212 241.795 9 782.938 246.197 778.121 243.105 10 782.423 246.302 778.152 242.956 11 545.692 498.817 545.454 498.707 12 545.420 497.978 545.210 498.081 13 544.821 498.164 545.387 497.998 14 549.760 155.548 546.673 156.030 15 548.061 216.444 545.203 220.138 16 547.123 280.189 545.112 284.178 17 546.739 342.886 545.084 348.794 18 545.286 404.469 545.230 413.049 19 544.014 467.282 545.013 477.326 20 542.886 530.045 546.101 541.485 21 541.821 592.255 544.800 605.823 22 540.931 654.616 544.037 669.866 23 539.097 717.196 543.792 734.005 24 537.240 779.850 543.653 798.783 25 534.042 841.975 544.153 851.045
Concerning the hardware, the operational slot demonstrated that the camera health status is nominal, including the mechanisms.
With respect to the operational procedures, this slot demonstrated again an excellent performance of the instrument, spacecraft and mission teams.
At mission level, we can confirm that no streak [RD4] was found in the images acquired during this operational slot. This does not mean that there are none, because the exposure times were so short that a streak, if present, would also be very short and easy to mistake for a high-energy particle hit. The FC team will continue to monitor the images acquired in flight in search for occurrences of streaks.
Finally, the observation of Canopus under different pointing conditions was successful and avoiding saturation enabled better determination of the position of the star compared to the earlier D034 observations. The quality of the data set is sufficient to determine the geometric co-alignment between FC and VIR.