Coating and surface finishing definition for the Solar Orbiter/METIS inverted external occulter
Bibliographic record
Abstract
The METIS coronagraph aboard the Solar Orbiter mission will undergo extreme environmental conditions (e.g., a thermal excursion of about 350 degrees throughout the various mission phases), due to the peculiar spacecraft trajectory that will reach a perihelion of 0.28 AUs. METIS is characterized by an innovative design for the occultation system that allows to halve the thermal load inside the instrument while guaranteeing the stray light reduction that is required for a solar coronagraph. The Inverted External Occulter (IEO) concept revolutionizes the classical scheme, by exchanging the usual positions of the entrance aperture (that is now the outermost element of the instrument facing the Sun) with the actual occulter (that is a spherical mirror inside the coronagraph boom). The chosen material for the IEO manufacturing is Titanium, as a trade o_ between light weight, strength and low thermal expansion coefficient. A 2 years long test campaign has been run to define the IEO geometry, and its results are addressed in previous dedicated papers. This work describes the results of a further campaign aimed at defining the IEO surface and edge finishing, the support flange geometry and the Titanium coating. Various edge finishing were installed on a prototype of the instrument occulting system and their performance in stray light reduction were compared. The support flange geometry was designed in order to reduce the overall weight, to control the thermal load and to accentuate its stray light suppression performance. The coating is a particularly delicate issue. A black coating is necessary in order to assess the stray light issues, typically critical for visible coronagraphs. Black coating of Titanium is not a standard process, thus several space qualified black coatings were experimented on Titanium and characterized. The impact of the IEO coatings was evaluated, the reflectivity and the BRDFs were measured and are addressed in the paper.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".