APEX-MPI-ICD-0002 Atacama Pathfinder Revision: 1.67 EXperiment Release: October 11, 2018 Category: 4 Interface Control Document Author: Dirk Muders Multi-Beam FITS Raw Data Format Dirk Muders, Edward Polehampton and Jennifer Hatchell The MBFITS working group: Robert Lucas [email protected] Helmut Wiesemeyer [email protected] Albrecht Sievers [email protected] Fr´ed´eric Gueth [email protected] Dirk Muders [email protected] Keywords: Data Format, FITS, APEX Author Signature: Dirk Muders Date: October 11, 2018 Approved by: L.˚A. Nyman Signature: L.˚A. Nyman Institute: APEX Date: October 11, 2018 Released by: L.˚A. Nyman Signature: L.˚A. Nyman Institute: APEX Date: October 11, 2018 APEX Multi-Beam FITS Raw Data Format Change Record Revision Date Author Section / Page affected; Summary Remarks 0.0 2002 J. Hatchell All Initial Version 1.3 2003-07-23 J. Hatchell All see ’What’s new in v.1.3’ 1.4 2003 J. Hatchell All see ’What’s new in v.1.4’ 1.51 2003 J. Hatchell All see ’What’s new in v.1.51’ 1.52 2003-12-18 J. Hatchell All see ’What’s new in v.1.52’ 1.53 2003-11-11 J. Hatchell All see ’What’s new in v.1.53’ 1.54 2004-08-09 J. Hatchell All see ’What’s new in v.1.54’ 1.55 2005-03-22 E. Polehampton All see ’What’s new in v.1.55’ 1.56 2005-09-15 E. Polehampton All see ’What’s new in v.1.56’ 1.57 2005-12-06 D. Muders 21, 40, 43, 56 see ’What’s new in v.1.57’ 1.6 2006-05-30 D. Muders 38, 39, 46, 50, 60, 61 see ’What’s new in v.1.6’ 1.61 2007-04-02 D. Muders Section 19.5.7, Keywords see ’What’s new in v.1.61’ 1.62 2007-08-14 D. Muders DATAPAR table structure, Keywords see ’What’s new in v.1.62’ 1.63 2011-08-05 D. Muders New keywords in several tables see ’What’s new in v.1.63’ 1.64 2013-10-18 D. Muders New keywords. Keyword iterations. see ’What’s new in v.1.64’ 1.65 2015-02-04 D. Muders New keywords. Long string keywords. see ’What’s new in v.1.65’ New optional DATAPAR column. 1.66 2017-12-14 D. Muders New keywords. see ’What’s new in v.1.66’ 1.66 2018-10-11 D. Muders Added HSSA pointing constant. see ’What’s new in v.1.67’ Create Date: October 11, 2018 Page 2 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format Contents 1 Introduction 8 1.1 MBFITS and ALMA-TI FITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.2 Scans, subscans and integrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2 What’s new in v.1.67? 10 3 What’s new in v.1.66? 11 4 What’s new in v.1.65? 12 4.1 Keyword changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1.1 SCAN-MBFITS table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1.2 FEBEPAR-MBFITS table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1.3 DATAPAR-MBFITS table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2 Table changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2.1 DATAPAR-MBFITS table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5 What’s new in v.1.64? 13 5.1 Keyword changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.1.1 SCAN-MBFITS table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.1.2 FEBEPAR-MBFITS table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.1.3 ARRAYDATA-MBFITS table . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6 What’s new in v.1.63? 14 6.1 Spectral axis descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.2 Keyword changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2.1 SCAN-MBFITS table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2.2 FEBEPAR-MBFITS table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2.3 DATAPAR-MBFITS table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.3 Additional Effelsberg keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.3.1 SCAN-MBFITS table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 7 What’s new in v.1.62? 16 7.1 Projection used in APEX MBFITS data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.2 Table changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.3 Keyword changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.4 MBFITS is a Registered Convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8 What’s new in v.1.61? 18 8.1 Az/El patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 9 What’s new in v.1.6? 19 9.1 MBFITS Hierachical Grouping Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 9.1.1 MBFITS Hierarchical Grouping Directory Structure . . . . . . . . . . . . . . . . 19 9.2 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 10 What’s new in v.1.57? 21 10.1 Switched observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 10.2 Array observing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 10.3 Other changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 11 What’s new in v.1.56? 22 11.1 Primary header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 11.2 Other minor changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Create Date: October 11, 2018 Page 3 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format 12 What’s new in v.1.55? 23 12.1 Feeds and backend ’sections’. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 12.2 Frequency scale axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 12.3 Observation → Subscan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 12.4 Additional Effelsberg changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 12.5 Minor changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 13 What’s new in v.1.54? 25 13.1 Array rotation: PC matrix, CRPIX and parallactic angle . . . . . . . . . . . . . . . . . . . 25 13.2 Observation → Subscan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 13.3 Minor changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 13.4 Additional Effelsberg parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 14 What’s new in v.1.53? 26 14.1 Revised documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 14.2 New keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 15 What’s new in v.1.52? 27 15.1 Types in ESO header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 15.2 Times for integrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 15.3 Frequency bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 16 What’s new in v.1.51? 28 16.1 FOCUS keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 16.2 ARRAYDATA to DATAPAR moves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 16.3 MJD, DATE-OBS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 16.4 Minor keyword changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 17 What’s new in v.1.4? 29 18 What’s new in v.1.3? 30 19 Explanatory notes 33 19.1 MJD, DATE-OBS and time system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 19.2 Scanning/mapping description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 19.3 Phase description for switched observations. . . . . . . . . . . . . . . . . . . . . . . . . . 34 19.4 Calibration parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 19.4.1 Continuum calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 19.4.2 Spectral line calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 19.5 WCS coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 19.5.1 Sources of spatial coordinate information . . . . . . . . . . . . . . . . . . . . . . 37 19.5.2 WCS representation and telescope control system input . . . . . . . . . . . . . . 38 19.5.3 WCS coordinate systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 19.5.4 30m parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 19.5.5 WCS parameters (including derivation from 30m parameters) . . . . . . . . . . . 41 19.5.6 Moving bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 19.5.7 Observations in Az/El . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 19.5.8 Pointing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 19.5.9 WCS spectral coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 19.5.10 Feeds and backend sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 20 References 47 Create Date: October 11, 2018 Page 4 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format 21 MBFITS specification 48 21.1 Data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 21.2 The Primary header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 21.3 The SCAN-MBFITS Binary Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 21.3.1 SCAN-MBFITS Binary Table Header Keywords . . . . . . . . . . . . . . . . . . . 51 21.3.2 SCAN-MBFITS Binary Table Columns . . . . . . . . . . . . . . . . . . . . . . . 58 21.4 The FEBEPAR-MBFITS Binary Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 21.4.1 FEBEPAR-MBFITS Binary Table Header Keywords. . . . . . . . . . . . . . . . . 59 21.4.2 FEBEPAR-MBFITS Binary Table Columns . . . . . . . . . . . . . . . . . . . . . 62 21.5 The ARRAYDATA-MBFITS Binary Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 21.5.1 ARRAYDATA-MBFITS Binary Table Header Keywords . . . . . . . . . . . . . . . . 64 21.5.2 ARRAYDATA-MBFITS Binary Table Columns . . . . . . . . . . . . . . . . . . . . . 66 21.6 The MONITOR-MBFITS Binary Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 21.6.1 MONITOR-MBFITS Table Header Keywords . . . . . . . . . . . . . . . . . . . . . 69 21.6.2 MONITOR-MBFITS Binary Table Columns . . . . . . . . . . . . . . . . . . . . . . 69 21.6.3 Anticipated monitor points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 21.7 The DATAPAR-MBFITS Binary Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 21.7.1 DATAPAR-MBFITS Binary Table Header Keywords. . . . . . . . . . . . . . . . . 73 21.7.2 DATAPAR-MBFITS Binary Table Columns . . . . . . . . . . . . . . . . . . . . . 75 21.8 The GROUPING Binary Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 21.8.1 GROUPING Binary Table Header Keywords . . . . . . . . . . . . . . . . . . . . . 77 21.8.2 GROUPING Binary Table Columns . . . . . . . . . . . . . . . . . . . . . . . . . . 77 21.8.3 Member File Primary Header Keywords . . . . . . . . . . . . . . . . . . . . . . 77 Create Date: October 11, 2018 Page 5 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format Abstract ThisdocumentdescribesaFITSrawdataformatformultibeammultireceiver/backendsingledish telescopes. It is intended for use at the IRAM 30m, Effelsberg 100m and APEX. Create Date: October 11, 2018 Page 6 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format Integrations Subscan Scan File (for each observation) H ... 2 1 ead ARRAYDATA table e r S ... ing FEBE 13 baseband ... Raw ba FEBE 13 baseban AR le file: s cken ds RAYD setObse PRIM d A ur A FE2 ba ... da FE2 ba TA pvin RY BE 2seban ta BE 2seban g HEA ds ds DE M R B S F C I R A T N S a MONITOR table w b m MO Hier loc ... on NI arc k stamps from ARRAInterpolation to bac itor data TOR FEBE 1F FEBE hically grouped files: diagram v.1.6 Yk E e B DATAnd timeFEBE 1FEBE...... DATAPAR table parameters Data associa FEBE 1FEBE DATAPAR E 2tabletable header GROUPING TAB PRIMARY HEAD 2 te 2 L E d E R by MJDentries are mand DATAPARRAYDA integrationper table rows header aAT tcRA h e d Figure 1: MBFITS file structure Create Date: October 11, 2018 Page 7 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format 1 Introduction 1.1 MBFITS and ALMA-TI FITS The MBFITS working group was created at the array receiver meeting at IRAM Grenoble in December 2001. The goal was to define a new raw data format for multibeam receivers based on FITS to be used at theIRAM30mandAPEXtelescopes. Withacommonrawdataformatitismucheasiertosharesoftware developments in the areas of data calibration (chopper wheel, atmospheric, etc.) and data reduction. The resultingMBFITSformatcanbeusedforallsingle-dishbolometerandheterodyneobservationsincluding multiple frontend/backend combinations and array receivers. The MBFITS format was derived structurally from the ALMA-TI FITS raw data format, although a numberofchangeshadtobemadetoaccommodatethespecialneedsoftheIRAMandAPEXtelescopes. We would like to thank especially Robert Lucas, who is one of the authors of the ALMA-TI format, for his valuable contributions to our discussions. TheMBFITSformatisbasedonthescan-subscan-integrationschemeusedbyALMA-TIFITSandretains manyofitskeywords. However,duetothechangesinstructureandadditionalkeywordsneededtoaccom- modate single-dish configurations, particularly multiple beam observing and multiple frontend/backend combinations, the MBFITS format can now be considered to be an independent format. In the subsequent sections we outline the updates in all the versions of MBFITS since release 1.3. In Sect. 19, various aspects of MBFITS are described in detail. Then follows the specification of the FITS tables (Sect. 21). Finally, we include references (Sect.20). 1.2 Scans, subscans and integrations ExtractedfromtheALMASoftwareGlossary(viaALMA-TIFITSdefinition,Lucas&Glendenning2001): dump Thesmallestintervaloftimeforwhichasetofcorrelateddatacanbeaccumulatedand output from the correlator. integration Asetofdumps,allidenticalinconfiguration(exceptfortheantennamotionand some others), that is accumulated and forms the basic recorded unit. subscan A set of integrations while the antennas complete an elemental pattern across the source, possibly while frequency switching, nutator switching, etc. (previous to v.1.54: observation) scan A set of subscans with a common goal, for example, a pointing scan, a focus scan, or an atmospheric amplitude calibration scan, or a correlation scan on a continuum source or a line source. For instance in the case of holography measurements a subscan would be a drift across the transmitterorabore-sightmeasurement,whileascancouldbethewholesetofsubscansneeded to acquire a beam map. Or a scan could be a pointing scan with two subscans (an azimuth drift and an elevation drift across the pointing calibrator) or an atmospheric calibration scan with three subscans (autocorrelations on the sky, and two loads at different temperatures, ...). A scan can be as simple as a short integration on a celestial source while total power and/or correlator output are recorded; or it could be a set of pointed subscans that are used together to form a map of an extended celestial source. Here are some examples of how this scheme works for single dish observing. Examples of a scan: – An on-the-fly map of an astronomical source, including associated sky off subscans – A raster map ... – A pointing scan (cross-raster or cross-OTF) – A focus scan – A skydip – A flux calibration measurement – Five on-source measurements forming a cross and a sky off position Create Date: October 11, 2018 Page 8 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format – A holography measurement ...and a subscan: – A line of an OTF map – One sample in a raster – A sample on a sky off position – A heterodyne calibration (HOT/COLD/SKY) – One step in a focus scan Create Date: October 11, 2018 Page 9 Contact author: Dirk Muders APEX Multi-Beam FITS Raw Data Format 2 What’s new in v.1.67? MBFITS 1.67 is a maintenance release adding just the HSSA pointing constant requested for the APEX pointing models. Create Date: October 11, 2018 Page 10 Contact author: Dirk Muders