1. Optical Telescope Assembly (OTA) specifications
| Optics type | Aplanatic Gregorian with heat dump mirror |
| Primary mirror | 50cm diameter aperture, light-weighted ULE |
| Primary-secondary mirror length | 1.5 m |
| Central obscuration ratio | 0.344 in radius |
| Effective F ratio | 9.055 at secondary focus |
| Collimator Lens (CLU) | 3cm diameter exit pupil, collimated in air |
| Polarization Modulator (PMU) | Continuous rotation, 1.6 sec/rotation retardation N ±0.35 waves at 630/517/525 nm |
2. Image stabilization system
| Correlation tracker | |
|---|---|
| CCD | 50"×50" pixel (0.22 arcsec / pixel) |
| Frame rate | 580 Hz |
| Spectral range | 629 - 634nm |
| Displacement Range | ±5 pixel |
| Error signal accuracy | 0.01" |
| Tip-tilt mirror and its control | |
| Signal used for closed loop control | Redidual signal from correlation tracker |
| Actuator | 3 Piezo actuators |
| Tilt range | 10.5" in radios on the sky |
| Control crossover frequency | 14 Hz (nominal gain) |
| Stability | < 0.02" (in laboratory environment) |
3. Broadband Filter Imager (BFI)
| Field of view | 218" × 109" (full FOV) | ||
|---|---|---|---|
| CCD | 4k × 2k pixel (full FOV), shared with the NFI | ||
| Spatial Sampling | 0.0541 arcsec/pixel (full resolution) | ||
| Spectral coverage | |||
| Center (nm) | Band width (nm) | Line of interest | Purpose |
| 388.35 | 0.7 | CN I | Magnetic network imaging |
| 396.85 | 0.3 | Ca II H | Chromospheric heating |
| 430.50 | 0.8 | CH I | Magnetic elements |
| 450.45 | 0.4 | Blue continuum | Temperature |
| 555.05 | 0.4 | Green continuum | Temperature |
| 668.40 | 0.4 | Red continuum | Temperature |
| Exposure time | 0.03 - 0.8 sec (typical) | ||
4. Narrowband Filter Imager (NFI)
| Field of view | 328"×164" (unvignetted 264"×164") | |||
|---|---|---|---|---|
| CCD | 4k×2k pixel (full FOV), shared with BFI | |||
| Spatial sampling | 0.08 arcsec/pixel (full resolution) | |||
| Spectral resolution | 0.009nm (90mÅ) at 630nm | |||
| Spectral windows (nm) and lines of interest | ||||
| Center | Tunable range | Lines | geff | Purpose |
| 517.2 | 0.6 | Mg I b 517.27 | 1.75 | Chromospheric Dopplergrams and magnetgrams |
| 525.0 | 0.6 | Fe 524.71 | 2.00 | Photospheric magnetograms |
| Fe I 525.02 | 3.00 | |||
| Fe I 525.06 | 1.50 | |||
| 557.6 | 0.6 | Fe I 557.61 | 0.00 | Photospheric Dopplergrams |
| 589.6 | 0.6 | Na I D 589.6 | - | Very weak fields (scattering polarization) Chromospheric fields |
| 630.0 | 0.6 | Fe I 630.15 | 1.67 | Photospheric magnetograms |
| Fe I 630.25 | 2.50 | |||
| Ti I 630.38 | 0.92 | Umbral magnetograms | ||
| 656.3 | 0.6 | H I 656.28 | - | Chromosphreic structure |
| Exposure time | 0.1 - 1.6 sec (typical) | |||
5. Spectro-polarimeter (SP)
| Field of view along slit | 164" (north-south direction) |
| Spatial scan range | ±164" |
| Slit width | 0.16" |
| Spectral coverage | 630.08nm - 630.32nm |
| Spectral resolution / sampling | 30mÅ / 21.5mÅ |
| Measurement of polarization | Stokes I,Q,U,V simultaneously with dual beams (orthogonal linear components) |
| Polarization signal to noise | 103 (with normal mapping) |
6. Observation controls and data handling
| Effective process speed of MDP | 832k pixels/sec (maximum for FPP data) | |
| Pixel depth compression by MDP | 16 bit to 12 bit, 8 lookup tables | |
| Image compression ratio (depends on images) |
12bit DPCM lossless | 6-8 bits/pixel |
| 12bit JPEG(DCT) lossy | <3bits /pixel for FG 1.5 bits/pixel for SP |
|
| Allocated telemetry rate for SOT | 1.3Mbps (nominal) 1.8Mbps (SOT dominant) |
|
| Average data rate | 300kbps (15 downlink contacts / day) | |