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Operational Capabilities and Scientific Data Production of the Solar-B SOT Instrument

This document provides an overview of the observational capabilities of the Solar-B SOT (Solar Optical Telescope) from an operational perspective. It covers the scientific data generation process via the Focal Plane Package (FPP) and how observations are managed through the SOT observation table in the Mission Data Processing (MDP) system. Key features include the macro-commands for capturing scientific data, various filters and magnetograms produced by the FG camera, and the Dopplergrams that measure line-of-sight velocities. This information is vital for understanding solar phenomena.

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Operational Capabilities and Scientific Data Production of the Solar-B SOT Instrument

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  1. SOT Scientific Observations & Operations Purpose: Look at SOT observational capabilities from operational viewpoints T. Shimizu (National Astronomical Observatory of Japan) Shimizu@solar.mtk.nao.ac.jp Some slides from Dr. T.Tarbell presented at 3rd science meeting 4th Solar-B Science Meeting

  2. Solar-B SOT On-board Operations • Scientific data are produced by Focal Plane Package (FPP) in SOT • Observational sequence is controlled by SOT observation table in MDP • FPP as a slave • Users update only the SOT observation table for their observations • Macro-command (MC) for taking a science data (observable) MDP Observation table (sequence) FPP Observation (observable generation) MC 4th Solar-B Science Meeting

  3. Sequence SOT Observation Table in MDP • Consists of FG table and SP table, which work independently each other • ProgramTable (Main routine) calls Subroutines which call Sequences which are lists of macro-commands and commands Obs. Program Main routine /w repeat # interval Subroutines Subroutines Subroutines Subroutines /w interval 100 sequences 20 programs 4th Solar-B Science Meeting

  4. Macro-commands • For taking a science data (observable) • Contain the following parameters which SOT chief observers may set up • Compression Parameters - MDP bit compression - MDP JPEG/DPCM compression • Operational Parameters • FG Extract Region or SP Map Region Parameters - Defining type of data (observable) (ex. Magnetogram,…) - CCD/exposure setup (ex. size, binning, exposure duration) - Wavelength setup (ex. l,l offset) etc 4th Solar-B Science Meeting

  5. Variety of SOT Data Solar-B SOT Scientific Data (Observables) from FPP Filtergraph (FG) Camera Filtergrams Broadband filter (G band, continuums etc) Narrowband filter (Ha), dark frame etc Longitudinal Magnetograms MC (Macro-command) Dopplergrams Issued from MDP observation tables (FG table and SP table) Stokes I/Q/U/V images Stokes-Polarimeter (SP) Camera Stokes Map 4th Solar-B Science Meeting

  6. FG Camera Observables: Filtergrams Solar-B Ha center G-band 4305 Filtergrams • 2-D spatial data (a snapshot image) • Size (typical): • 2K x 4K pixels (max) • 2K x 2K • 1K x 1K • 0.5K x 0.5K (from combination of FOV size + pixel sum) • Full size FOV: Broadband filter 164”x328” • Narrowband filter 109”x218” • Pixel sum: 1x1(full), 2x2, 4x4 4th Solar-B Science Meeting

  7. FG Camera Observables: Filtergrams Solar-B Filtergrams • Wavelength (typ.) • Broadband filter (6) • CN I 3883, CaII H 3969, CH I 4305, Continuum 4505 • Continuum 5551, Continuum 6684 • Narrowband filter • various l positions in Ha 6563, HeNe, (and bands including • lines mainly used for Magneto/Dopper-grams) • Dark frame • l scan filtergrams (X x Y pixels) x N (N= # of l scan) 4th Solar-B Science Meeting

  8. Filtergrams (NFI & BFI) • Shutter open/close always synchronized with Polarization Modulator • Exposure times 0.1 - 1.6 sec in NFI, .03 - .8 sec in BFI (longer exposures possible if desired) • Full readout in 3.4 sec, 2x2 summing in 1.7 sec, 4x4 summing 0.9 sec • Partial readout possible for faster cadence & reduced data volume: several discrete sizes from 192 to 2048 rows • Reconfigure time (filterwheels, TF) < ~2.5 sec • No onboard processing in FPP, optional data compression in MDP

  9. FG Camera Observables: Magnetograms Solar-B Longitudinal Magnetograms • 2-D spatial data generated on-board from multiple exposures • Maps of Stokes V / Stokes I • Using multiple wavelengths reduces errors caused by Doppler shifts • Processing onboard combines many images into two (numerator & denominator) for reduced telemetry requirement 4th Solar-B Science Meeting

  10. FG Camera Observables: Magnetograms Solar-B Longitudinal Magnetograms • Primary lines are Fe I 6302.5 (photosphere) and Mg I 5172.7 (low chromosphere) • 5250.2, 5250.6, 5247.1, 6301.5, 6303.8 (umbral) are also available • 6302 Mgram with 0.08 arcsec px takes ~21 sec for 8 images (4 wavelengths) with 164x164 arcsec FOV, has rms noise of ~1.E15 Mx on a pixel • With 0.16 arcsec px, takes 12.8 sec and has rms noise ~2.E15 Mx • Size (typical): • 1K x 2K x N (smart memory limit) • 1K x 1K x N • 0.5K x 0.5K x N • (N= 2 [Magnetogram V and I]) or 1) • (from combination of FOV size + pixel sum) 4th Solar-B Science Meeting

  11. FG Camera Observables: Dopplergrams Solar-B Dopplergrams 4th Solar-B Science Meeting

  12. Dopplergrams • Maps of line-of-sight component of velocity • Baseline is simplified version of algorithm used by MDI instrument on SOHO • Derive central wavelength from 4 images uniformly spaced through the line, F1 ... F4 • R = (F1 + F2 - F3 - F4) / (F1 - F2 - F3 + F4) • Velocity = V(R), implemented on the ground by lookup-table • Use 2 smart memories to make numerator & denominator • Gain and offset variations of CCD cancel out • MDP performs compression & downlink • Best photospheric line is Fe I 5576 (non-magnetic, g=0) • 1-sigma noise of 30 m/s with 4 images, 2x2 summing, 0.16 arcsec px, 0.8 sec exposure, 240,000 electrons/px, 12.8 sec total time • 1-sigma noise of 45 m/s with 0.08 arcsec px, 1.6 sec exposure • Low chromospheric velocity can be measured in core of Mg I 5173 line • Very dark line, but higher velocities expected • 1-sigma noise ~ 100 m/s with 0.16 arcsec px, 1.6 sec exposures

  13. FG Camera Observables: Stokes Solar-B Stokes IQUV Stokes IV Stokes IQ Stokes IU • A set of 2-4 different images of 2-D spatial data generated on-board • from multiple exposures • Size (typical): • - Shuttered exposures 1K x 1K x N pixels • 0.5K x 0.5K x N • - Shutterless exposures 1K x 256 x N • 1K x 128 x N (N= 4 or 2) • (from combination of FOV size + pixel sum) • Wavelength (typ.) • Mg Ib 5173, Fe I 5247, Fe I 5250, Fe I 5251, • Fe I 6302, Fe I 6303, Ti I 6304 • Integration # of Exposures 4th Solar-B Science Meeting

  14. Stokes Parameters • Shutterless imaging with FOV restricted by focal plane mask • 0.1 sec exposure and readout time: IQUV all measured simultaneously • FOV = 5.3 x 164 for 0.08 arcsec pixels, 14.7 x 164 for 0.16, 35 x 164 for 0.32 • Processing in smart memories identical to that for SP, to make spatial maps of I, Q, U, and V • 0.2 sec exposure and readout time: IQV or IU, measured separately • FOV = 10.7 x 164 for 0.08 arcsec pixels, 29 x 164 for 0.16, 70 x 164 for 0.32 • Measure I & Q first, then I & U by shifting phase of exposure wrt Pol. Mod. • 0.4 sec exposure and readout time: IV only • FOV = 21 x 164 for 0.08 arcsec pixels, 58 x 164 for 0.16, or 140 x 164 for 0.32 • Stokes Parameters using shutter • Up to 0.4 sec exposures possible for V, up to 0.2 sec for Q & U • Additional noise sources due to time between frames & cross-talk between polarizations will appear

  15. SP Camera Observables Solar-B I Q U V Stokes Map • 4 images at one scan position • generated from multiple • exposures (typically 48) • Wavelength • Fe I 6302 & 6303 Scanning step (1~2K) 1024 (max) • Size (typical): • One Stokes: 1K x 224 pixels • Map: 1K x 224 x 2K pixels • 896M bytes (without compression) • 135M bytes (15% compression) • Integration # of Exposures • Map center position and # of slit scan positions • Slit scan step size/pixel binning & slit scan summation • Tip-tilt mirror (CTM) reset, repeat observation 112 or 224 (/w orthogonal) 4th Solar-B Science Meeting

  16. Spectro-Polarimeter Observing Modes (1 of 2) • Normal Observing Mode • Expose/Read/Demodulate for 3 full rotations of waveplate, producing polarimetric accuracy of 0.001 • Optionally, move the slit-scanning mirror one step of 0.16 arcsec in the solar image (this takes 0.1 or 0.2 sec ==> 5.0 sec cycle) • Raw data is 120 x 2 spectral pixels x 1024 spatial pixels x 4 Stokes parameters in 4.8 sec, which is 983 Kpixels or 205 Kpixels/sec • Send to MDP for optional compression and downlink • Maps area 1.6 arcsec wide in 50 sec or 160 arcsec wide in 83 min. • Fast Map Mode • Expose/Read/Demodulate for 1 full rotation of waveplate, step the slit 0.16 arcsec, Expose/Read/Demodulate for a 2nd rotation, adding to the previous results • Sum 2 pixels in spatial direction on chip ==> effective pixel size is 0.32 x 0.32 arcsec • Raw data rate is 492 Kpixels in 3.6 sec = 137 Kpixels/sec • Maps area 1.6 arcsec wide in 18 sec, and 160 arcsec in 30 min 4th Solar-B Science Meeting

  17. SP Observing Modes (2 of 2) • In any mode, Field-of-View and data rate can be restricted by sending to the MDP only spectra from a limited spatial portion of the slit • Dynamics Mode • Expose/Read/Demodulate for only 1 full rotation of waveplate • Optionally step the slit by 0.16 arcsec • Must limit spatial FOV to reduce data rate: maybe 32 arcsec typical slit length • Process as before • For 32 arcsec along the slit, raw data rate is 192 Kpixels in 1.6 sec or 120 Kpixels/sec • Deep Magnetogram Mode • Expose/Read/Demodulate for many full rotations of waveplate • Goal is to detect weakest polarization signals possible • Ignore wrap-around of intensity and strong polarization signals • Downlink data with no compression to avoid artifacts from wrap-around boundaries 4th Solar-B Science Meeting

  18. SW Tools for Observation Planning • SOT chief observers need SW tools to make macro-commands & program/sequence tables (or reuse existing ones in the database) to carry out a scientific observation • Detailed design/task sharing is under discussion • An example for macro-command editor used now in FPP flight-model test 4th Solar-B Science Meeting

  19. For editing SP macro-commands 4th Solar-B Science Meeting

  20. For FG macro-command 4th Solar-B Science Meeting

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