Document Number: SC2/FTS/SOF/020

Size: px

Start display at page:

Download "Document Number: SC2/FTS/SOF/020"

Virgil Curtis
5 years ago
Views:

1 SCUBA-2 FTS Project Office University of Lethbridge Physics Department 4401 University Drive Lethbridge, Alberta CANADA T1K 3M4 Tel: Fax: WWW: Document Title: FTS-2 Data Flow Diagrams Document Number: SC2/FTS/SOF/020 Issue: Draft Version 0.3 Date: 6 February 2007 Document Prepared By: B. G. Gom FTS Project Manager Signature and Date: 06/02/07 Document Approved By: Document Released By: D. A. Naylor FTS Project Lead J. Molnar Canadian Project Manager Signature and Date: Signature and Date: 06/02/07 06/02/07 Page 1 of 7

2 Change Record Issue Date Section(s) Affected Description of Change / Change Request Reference / Remarks 0.1 2/02/07 All First draft 0.2 5/02/07 Removed link to radiometer 0.3 6/02/ typo: SED mode will use the dual-port configuration Contents Change Record... 2 Contents Introduction Data Flow Diagrams Overall FTS-2 Data Reduction ZPD Mode SED Mode High Resolution ( Line) Mode... 7 Page 2 of 7

1. Introduction This document presents the Data Flow Diagrams for the FTS-2 processing, when used in the operating modes described in the FTS-2 Use Cases document (SC2/FTS/SYS/021).

3 1. Introduction This document presents the Data Flow Diagrams for the FTS-2 processing, when used in the operating modes described in the FTS-2 Use Cases document (SC2/FTS/SYS/021). These diagrams are only meant to show the types of information that flow between the various systems and stages in the processing sequence. In these diagrams, data flows along the arrows between symbols as defined below: Symbol Meaning Data process Multiple process, possibly involving several processing steps External interactor Data store Page 3 of 7

4 2. Data Flow Diagrams 2.1. Overall FTS-2 Data Reduction At the top level, the FTS-2 data reduction consists of transforming recorded interferograms into spectra which are displayed on the observer quicklook display and saved in the data archive. The spectra must be calibrated in both frequency scale and amplitude, using information about the instrumental phase, the atmospheric transmission, telescope beam profile and the detector spectral responsivity. DRAMA commands from DR Recipes s Page 4 of 7

5 2.2. ZPD Mode The ZPD operating mode records a short double-sided interferogram with the FTS configured in the single-port mode and one of the blackbody shutters closed. The resulting interferogram contains information of the offset of the moving mirror translation stage encoder, as well as non-linear phase introduced by the beamsplitters and electronics. The phase is calculated from the interferogram data and fit to a polynomial approximation. The polynomial terms are saved in a calibration database for use in reducing interferograms recorded in the SED or Line modes. A 2D image of the calculated ZPD offsets is also produced, which is a useful diagnostic tool for checking the instrument stability before a run. This image, and flags for any pixels with ZPD offsets larger than expected, is displayed to the observer. Page 5 of 7

2.3. SED Mode The SED observation mode produces low-resolution double-sided interferograms using the dual-port configuration, which are processed into spectral cubes which can then be processed

6 2.3. SED Mode The SED observation mode produces low-resolution double-sided interferograms using the dual-port configuration, which are processed into spectral cubes which can then be processed further to be displayed as SED maps of the FTS-2 FOV. The interferograms are first processed into spectra with the FTS-2 DR Engine, corrected for instrumental and atmospheric effects, and then transformed into the proper coordinate frame. Nodding may be considered after commissioning, which will involve a processing step to subtract the appropriate spectral cubes. The data will be displayed as either the corrected spectra, or the fully reduced SED maps. The SED calculation algorithm is still under development, and may involve information from both bands or just the 850 μm band. FTS-2 SED Mode Data Reduction Data Flow Diagram SCUBA-2 Pipeline SED Mode Reduce to Spectra ZPD Offset Database Wavelength and Responsivity Scale Factors PWV File Headers Calibrated Phase Fit Quality Derotation and Coordinate Transform s s Optional Nodding Subtraction s Data Archive Compute SED MAP SED Image Observer Display SED Image 1D Spectra Process QL Display Page 6 of 7

7 2.4. High Resolution ( Line) Mode The Line mode acquires high-resolution single-sided interferograms using the dual-port configuration. It is likely that the normal phase correction algorithm will fail in the dual-port mode, so previously stored phase correction parameters may be used instead (eg from the ZPD mode). If the normal phase correction procedure is used, the quality of the phase fit can be displayed as a diagnostic parameter. The products of this mode are spectral cubes which have been corrected for instrumental and atmospheric effects and transformed into the appropriate coordinate frame. The observer display will consist of spectra for individual pixels, or 3D visualization of the entire spectral cube. FTS-2 Hi-Res Mode Data Reduction Data Flow Diagram SCUBA-2 Pipeline Hi Res Mode Reduce to Spectra Phase Fit Parameters Database Wavelength and Responsivity Scale Factors PWV File Headers Phase Fit Quality Calibrated Derotation and Coordinate Transform s Data Archive Observer Display 3D Visualization 1D Spectra Process QL Display Optional Nodding Subtraction Page 7 of 7

Document Number: SC2/FTS/OPT/002

Document Number: SC2/FTS/OPT/002 SCUBA-2 FTS Project Office University of Lethbridge Physics Department 4401 University Drive Lethbridge, Alberta CANADA T1K 3M4 Tel: 1-403-329-2771 Fax: 1-403-329-2057 Email: brad.gom@uleth.ca WWW: http://research.uleth.ca/scuba2/