1 m F/6 Cassegrain NIR Telescope — Concept Trade Study

• Config: config/telescope.yaml
• Orbit model: SSO LEO proxy, period 5760 s, Earth IR 237 W/m^2 (Teff ~ 254.3 K)

Optics

• Primary diameter: 1.000 m
• Effective focal length: 6.000 m (F/6.00)
• Primary focal length: 2.200 m (F/2.20)
• Secondary magnification: 2.727
• Primary conic: K = -1.000, R = 4.400 m
• Secondary conic: K = -4.657, R = 2.288 m
• Primary clear aperture: 1.000 m
• Secondary clear aperture: 0.344 m (obscuration ratio ~ 0.344)
• Primary-secondary separation: 1.476 m
• Back focal distance: 0.500 m
• Alignment tolerances: +/-40 um spacing, +/-25 um decenter, +/-15 arcsec tilt, +/-30 um detector focus
• Plate scale: 34.377 arcsec/mm
• Airy radius (first zero): 7.32 um @ 1.0 um, 14.64 um @ 2.0 um

Thermal design (parametric)

• Targets: optics <= 150 K, detector <= 100 K (hot steady-state)
• Sunshield layers: 4, radius 2.50 m
• V-groove layers: 3
• Radiator area: 5.00 m^2, Earth view factor 0.0020
• MLI effective emissivity (between sunshield layers): 0.0200
• Bus->cold conductive leak: 0.010 W/K
• Structure->optics conduction: 0.050 W/K
• Structure->radiator conduction: 0.400 W/K
• FPA->detector conduction: 0.050 W/K
• Telescope Earth view factor: 0.0200
• V-groove view factors: space 0.70, Earth 0.01

Stray light (direct-path proxy)

• Baffle acceptance half-angle (proxy): ~7.0 deg
• With Sun keep-out >= 85 deg, direct Sun rays cannot traverse the optical tube to the focal plane in this proxy model.

Thermal results (steady-state)

• hot1: primary 113.0 K, secondary 110.9 K, detector 91.0 K, radiator 86.6 K
• hot2: primary 101.7 K, secondary 100.6 K, detector 85.6 K, radiator 81.7 K
• cold1: primary 93.6 K, secondary 94.2 K, detector 82.6 K, radiator 78.9 K
• degradation1: primary 111.8 K, secondary 109.3 K, detector 90.2 K, radiator 85.7 K

Survival heaters (cold-case sizing)

• Detector free-float in cold case: 82.6 K; hold at 90 K requires ~2.35 W

Thermal results (transient, one orbit)

• Detector: min 90.6 K, max 90.6 K
• Primary: min 112.1 K, max 112.1 K

View-factor verification

• Small emitter disk (~point) to receiver disk on-axis: analytic 0.409836, MC 0.410870, rel err 0.252% (200000 samples)

Limitations

• Lumped-node thermal network; geometry view factors are coarse and intended for early trades.
• Optical ray tracing is paraxial plus exact conic reflections in one meridional plane; the repo now carries a screening-level STOP/WFE gate tied to the released thermal/mechanical outputs, but full 3D wavefront propagation and multi-bounce scatter remain open.
• Stray light check is direct-path only; no multi-bounce BRDF/scatter model yet.