Per user preference: terse, physically-structured, no caveats. Organized by document, specs vs. measured values separated.
Source documents¶
- 2405.13493v1 — Jahnke et al., "The Euclid NISP instrument" (A&A) — main reference, overview + as-built design
- 2506.08378v2 — Gillard et al., "The NISP spectroscopy channel, on ground performance and calibration" (A&A) — ground PSF/spectro calibration
- 2303.09130v1 — SPIE proc., NISP grism FM (LAM), grism WFE test campaign
- aapg-2022-Trame_proposition_detaillee.docx — internal ANR/DISPERS proposal, summary-level, less authoritative for numbers than the peer-reviewed papers
1. Telescope¶
| Item | Value | Type | Source |
|---|---|---|---|
| Design | Korsch off-axis TMA (three-mirror anastigmat) | spec | Jahnke+2024 |
| Primary mirror diameter | 1.20 m | spec | Jahnke+2024 |
| Off-axis chief-ray angle onto NISP FPA | 0.8357° to M1 axis | design value | Jahnke+2024 |
| Telescope F-ratio (input to NISP) | F/20.4 → NISP F/10.4 | spec | Jahnke+2024 |
| Wavefront error criterion | Maréchal: WFE RMS < λ/14 (diffraction-limited) | requirement | Jahnke+2024 |
| Orbit | Sun–Earth L2 | spec | Jahnke+2024 |
2. NISP instrument — top-level¶
| Item | Value | Type | Source |
|---|---|---|---|
| FOV | ~0.5–0.57 deg² (0.7 deg² per DOCX) | spec (values differ slightly between sources — 0.57 deg² Jahnke+2024 is authoritative) | Jahnke+2024 / DOCX |
| Plate scale | 0.3″/pix | spec | Jahnke+2024 |
| FPA | 4×4 H2RG (HgCdTe), 2040×2040 science px + 4-px reference border | spec | Jahnke+2024 |
| Pixel pitch | 18 µm | measured | Jahnke+2024 |
| Detector operating temp | ~95 K | spec/measured | Jahnke+2024 |
| Detector cutoff wavelength | 2.3 µm (vs 2.5 µm for JWST NIRCam) | spec | Jahnke+2024 |
| Volume | 100×50×50 cm | spec | Jahnke+2024 |
| Mass budget (main structure) | 37 kg allocation | spec | Jahnke+2024 |
| Total mass | max 155 kg; actual 85.3 kg (instrument) + 40.7 kg (warm electronics) | spec / measured | Jahnke+2024 |
| Power | max 200 W | spec | Jahnke+2024 |
| First eigenfrequency | > 80 Hz target | requirement | Jahnke+2024 |
| Thermo-mechanical stability (optics) | < 0.3 K over 6 yr | requirement | Jahnke+2024 |
| Detector thermal stability | ≤ 4 mK over ~1200 s (req); measured 1 mK RMS (FPA), 2 mK RMS (optics) in PV | spec vs. measured | Jahnke+2024 |
| Downlink data rate | allocation 290 Gbit/day; measured ~31 ± 3 GB/day (20 ROS × 4 dithers) ≈ 248 Gbit/day | spec vs. measured | Jahnke+2024 |
| Radiator temps | ~130 K (structure/optics), ~95 K (detectors) | design | Jahnke+2024 |
| Thermal env. (instrument cavity) | 130–135 K | measured | Jahnke+2024 |
| NI-CU illumination angle | ~12° (axis to FPA vs FPA normal) | design | Jahnke+2024 |
3. NISP-P photometric passbands (Table 1, Jahnke+2024, from Schirmer+2022)¶
| Filter | 50% cut-on [nm] | 50% cut-off [nm] | centre [nm] | σ50 (centre/corner) [nm] | σcen [nm] |
|---|---|---|---|---|---|
| YE | 949.6 | 1212.3 | 1080.9 | 0.8/0.8 | 0.6 |
| JE | 1167.6 | 1567.0 | 1367.3 | 0.8/0.9 | 0.6 |
| HE | 1521.5 | 2021.4 | 1771.4 | 0.8/0.9 | 0.6 |
Out-of-band blocking factor: in-band 10⁻⁴; out-of-NISP-range 10⁻⁵–10⁻⁹. Photometric contamination: ≤2 mmag (typ. 0.2 mmag). — all measured.
4. Grisms (Table 2, Jahnke+2024)¶
| Parameter | RGS000/180 | RGS270 | BGS000 |
|---|---|---|---|
| FWHM bandpass [nm] | 1206–1892 | (same) | 926–1366 |
| Prism angle A | 2.145° ± 30″ | — | 1.77° ± 30″ |
| Groove height H [µm] | 3.16 ± 0.08 | — | 2.25 ± 0.1 |
| Blaze angle β | 2.49° | 2.48° | 1.94° |
| Groove pitch [µm] | 72.55 | 72.96 | 66.22 |
| Groove density [mm⁻¹] | 13.75 | 13.7 | 15.1 |
| 0th-order transmission | 2.4% | 2.3% | 2.0% |
| 1st-order transmission | 84.7% | 84.3% | 84.2% |
| dλ/dx [nm/pix] | +1.372 (RGS000), −1.372 (RGS180) | — | 1.239 |
| R (resolving power) | > 480 (RGE) | — | > 400 (BGE) |
All measured (ground). Requirement was R ≥ 380 (BGE)/R ≥ 480 (RGE per some sections — check consistency: overview §2 states R ≥ 380 generically as requirement; Table 2/§3.4 gives measured R>480 RGE, R>400 BGE — the measured values exceed requirement).
Redshift-error requirement: σ(z) < 0.001(1+z) for Hα, FWHM 0.5″ source, 3.5σ flux limit ≤2×10⁻¹⁶ erg cm⁻² s⁻¹ — specification, consistent with Table 5 limiting sensitivity ~2×10⁻¹⁶ (measured, in-flight initial estimate).
Grism material: Suprasil 3001, OH+metallic impurities <1 ppm (spec).
Grism WFE metrology (2303.09130v1, Table 1 — LAM FM test campaign, measured vs. spec)¶
- Transmitted WFE spec < 20 nm RMS @633 nm → measured 10–12 nm RMS (compliant, all 4 FM units)
- Grating surface RMSi spec <30 nm RMS → measured 25.5–27 nm RMS (RGS000/180/270, compliant); BGS000 37.4 nm RMS (non-compliant)
- Filter surface RMSi spec <15 nm RMS → measured 3–10.5 nm RMS (compliant, all units)
- Focus defocus spec ±0.5 fringe → BGS000 0.61 fr (non-compliant); others compliant (0.05–0.34 fr)
- Curvature-after-gluing spec ≤5 fr shift → RGS000, RGS180 non-compliant (5.23–8.4 fr); RGS270, BGS000 compliant (4.18–4.63 fr)
- Overall: efficiency >70% on bandpass, WFE on surfaces <30 nm RMS (summary claim, slightly looser than per-unit table)
- Vibration qualification: withstood up to 11.6 g RMS random; cryo-vac test to 130 K
Discrepancy note: 2303.09130v1 states spectral transmission requirement "better than 65%," achieved >70%; Jahnke+2024 gives measured 1st-order transmission 84–85%. Both consistent (different measurement stage: component-level vs. as-integrated FM), 2405.13493v1 more authoritative as later, instrument-level, published account.
5. FPA / detector chain (Table 3 & 4, Jahnke+2024 — measured, CPPM/IP2I/LAM campaigns)¶
- QE (median over 16 SCA), accuracy ±5% (absolute, Waczynski+2016): YE 88–96%, JE 93–98%, HE 93–99%
- Read noise: Spectro mode 7.7–9.2 e⁻; Photo mode 5.6–6.7 e⁻ (medians per SCA)
- Disconnected pixels: 135–3223 per detector (missing/faulty indium bumps)
- Dark current: ~0.02 e⁻ s⁻¹ pixel⁻¹ (measured)
- Cross-talk amplitude: ~0.001% (measured, ground)
- IPC central-pixel loss: 2.87 ± 0.01% (Le Graët+2022, measured)
- Baseline pedestal: ~5.5 kADU (reference px), ~10 kADU (science px); temp. dependence ~−120 ADU/K (measured)
- Exposure synchronization across 16 detectors: <10 ns (spec, achieved)
- QE 5th-percentile spectral curve: Fig. 12 (measured at NASA JPL)
6. PSF (in-flight, Table 5, Jahnke+2024 — "initial in-flight estimates," measured)¶
| Filter | rEE50 | rEE80 | FWHM | ZP [AB] | Lim. sens. |
|---|---|---|---|---|---|
| YE | 0.22″ | 0.37″ | 0.35″ | 24.95 | 24.6 mag (5σ) |
| JE | 0.24″ | 0.45″ | 0.34″ | 25.19 | 24.6 mag |
| HE | 0.27″ | 0.55″ | 0.35″ | 25.11 | 24.5 mag |
| BGE | 0.21″ | – | – | – | N.A. |
| RGE | 0.24″ | – | – | – | ~2×10⁻¹⁶ erg s⁻¹cm⁻¹ (3.5σ, 2×13.4 Å width) |
Range quoted in text: rEE50 0.21″–0.27″, rEE80 0.37″–0.55″ across bands.
Optical-only (lab, 960 nm, NI-OA, pre-detector) EE: ~2/3 energy within R=0.5 px — measured, ideal diffraction-limited case only few % better.
Ground grism PSF (2506.08378v2, measured, no telescope PSF included)¶
- EE50 ≈ 0.6 × requirement (<0.3″ at 1500 nm) → i.e., measured EE50 well inside spec
- Rotational misalignment tolerance tested: ±4°, no measurable EE50/EE80 change
- These ground values exclude telescope contribution — not directly comparable to in-flight Table 5 numbers without added telescope PSF/jitter terms.
7. In-flight PSF broadening budget (Jahnke+2024, reasoning + measured contributions)¶
Relative to lab optical PSF at 960 nm: - YE central λ 1081 nm → ~13% larger PSF (diffraction scaling, λ-driven) - Pointing jitter: ~35 mas (measured, spacecraft) - IPC: broadens further (see §6 above, 2.87% central-pixel effect) - BFE: additional broadening, flux-dependent (brighter stars more affected) — qualitative in this paper, no BFE amplitude number given here.
Inconsistency flagged: FOV value differs (0.57 deg² Jahnke+2024 vs. 0.7 deg² in the DOCX proposal) — the peer-reviewed Jahnke+2024 number is authoritative; the DOCX is a project-internal summary document, lower priority per source hierarchy.
Gap: No BFE (brighter-fatter effect) magnitude, no explicit VIS-instrument quantitative table, found in the provided documents — VIS specs mentioned only qualitatively (530–920 nm passband) via citation to Cropper et al./Euclid Collaboration: Cropper et al. 2024, not itself in the library.