Testing the Ariel exoplanet space observatory
<p>Ariel is an ESA mission that will use the transit spectroscopy method to observe the atmospheres’ of ~1000 exoplanets. Ariel is a 1 m class cryogenic space telescope that will be placed in a halo orbit around the Earth-Sun L2 point. To detect atmospheric molecular absorption features, Arie...
| Main Author: | |
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
2023
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| _version_ | 1826312830270308352 |
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| author | Spry, R |
| author2 | Bowles, N |
| author_facet | Bowles, N Spry, R |
| author_sort | Spry, R |
| collection | OXFORD |
| description | <p>Ariel is an ESA mission that will use the transit spectroscopy method to observe the atmospheres’ of ~1000 exoplanets. Ariel is a 1 m class cryogenic space telescope that will be placed in a halo orbit around the Earth-Sun L2 point. To detect atmospheric molecular absorption features, Ariel will produce medium-resolution spectra (R ≥ 15) using three spectroscopic channels covering 1.1 – 7.9 µm as well as having photometric channels covering 0.5 – 1.1 µm. The technical driver for Ariel, though, is the photometric stability. This is to enable the detection of atmospheric spectral features that are a signal of tens of ppm relative to the host star. Ariel, therefore, aims to have tens of ppm stability over long (10 hr) timescales.</p>
<p>To achieve Ariel’s science goals, the payload requires detailed calibration and performance verification. The testing of the integrated Ariel payload will be the subject of this work. The ground calibration of the Ariel payload will take place in 2026 in the 5m vacuum chamber at the Rutherford Appleton Laboratory’s space instruments test facility. The payload will be enclosed in a Cryogenic Test Rig (CTR), to provide a space-like (35 K) thermal environment. During the cryogenic vacuum testing, the payload will be illuminated by the Optical Ground Support Equipment (OGSE). The OGSE used to calibrate the payload is being developed by a team led by Oxford University and the University of Lisbon.</p>
<p>The author joined the project just before mission adoption. The thesis was submitted just after the completion of the payload Preliminary Design Review (pPDR). The work completed in this thesis focused, therefore, on performance simulation, requirement derivation and design of the OGSE system. In this thesis, many of the key performance parameters will be derived. It will be shown how these parameters have shaped the OGSE system from an architectural level down to the detailed design.</p>
<p>To define the performance parameters of the OGSE, the calibration observation modes must be defined. Methods were, therefore, defined to show how the OGSE can be used to perform the payload-level calibration of Ariel. End-to-end radiometric simulations were also provided to simulate the focal plane signal when the payload is illuminated in the various calibration modes of the OGSE.</p>
<p>The photometric stability and dark current tests were identified as particular drivers for the OGSE design. The need for dark testing of the payload was used to derive the thermal requirements for the system. Finite Element Analysis (FEA) was then used to assess the thermal performance of the OGSE system, and thus enable low-background testing of the payload (<1 e-pix-1s-1 ). The other performance driver identified was the photometric stability test. End-to-end time-domain simulations of this test were performed to derive the required performance of OGSE flux monitoring systems. OGSE monitoring detector candidates were then assessed to demonstrate these could be used to verify the stability of the payload.</p>
<p>Alignment during ground testing was discovered to be a critical technical risk to the OGSE system. It will be shown how monitoring alignment from ambient to cryogenic temperatures led to a major redesign of the OGSE architecture. Moreover, Ariel’s tiny field of view (~30’’) leads to extreme (arcsecond) alignment maintenance requirements. An alignment monitoring system will be presented, built and verified, to enable the closed-loop monitoring required to keep the OGSE spot within the payloads’ spectrometer slits.</p> |
| first_indexed | 2024-09-25T04:01:14Z |
| format | Thesis |
| id | oxford-uuid:0f430330-e931-49e5-b986-0f7fc7ccd9b2 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:01:14Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | oxford-uuid:0f430330-e931-49e5-b986-0f7fc7ccd9b22024-05-03T14:33:39ZTesting the Ariel exoplanet space observatoryThesishttp://purl.org/coar/resource_type/c_db06uuid:0f430330-e931-49e5-b986-0f7fc7ccd9b2EnglishHyrax Deposit2023Spry, RBowles, NNowicki, KGrainger, DSavini, G<p>Ariel is an ESA mission that will use the transit spectroscopy method to observe the atmospheres’ of ~1000 exoplanets. Ariel is a 1 m class cryogenic space telescope that will be placed in a halo orbit around the Earth-Sun L2 point. To detect atmospheric molecular absorption features, Ariel will produce medium-resolution spectra (R ≥ 15) using three spectroscopic channels covering 1.1 – 7.9 µm as well as having photometric channels covering 0.5 – 1.1 µm. The technical driver for Ariel, though, is the photometric stability. This is to enable the detection of atmospheric spectral features that are a signal of tens of ppm relative to the host star. Ariel, therefore, aims to have tens of ppm stability over long (10 hr) timescales.</p> <p>To achieve Ariel’s science goals, the payload requires detailed calibration and performance verification. The testing of the integrated Ariel payload will be the subject of this work. The ground calibration of the Ariel payload will take place in 2026 in the 5m vacuum chamber at the Rutherford Appleton Laboratory’s space instruments test facility. The payload will be enclosed in a Cryogenic Test Rig (CTR), to provide a space-like (35 K) thermal environment. During the cryogenic vacuum testing, the payload will be illuminated by the Optical Ground Support Equipment (OGSE). The OGSE used to calibrate the payload is being developed by a team led by Oxford University and the University of Lisbon.</p> <p>The author joined the project just before mission adoption. The thesis was submitted just after the completion of the payload Preliminary Design Review (pPDR). The work completed in this thesis focused, therefore, on performance simulation, requirement derivation and design of the OGSE system. In this thesis, many of the key performance parameters will be derived. It will be shown how these parameters have shaped the OGSE system from an architectural level down to the detailed design.</p> <p>To define the performance parameters of the OGSE, the calibration observation modes must be defined. Methods were, therefore, defined to show how the OGSE can be used to perform the payload-level calibration of Ariel. End-to-end radiometric simulations were also provided to simulate the focal plane signal when the payload is illuminated in the various calibration modes of the OGSE.</p> <p>The photometric stability and dark current tests were identified as particular drivers for the OGSE design. The need for dark testing of the payload was used to derive the thermal requirements for the system. Finite Element Analysis (FEA) was then used to assess the thermal performance of the OGSE system, and thus enable low-background testing of the payload (<1 e-pix-1s-1 ). The other performance driver identified was the photometric stability test. End-to-end time-domain simulations of this test were performed to derive the required performance of OGSE flux monitoring systems. OGSE monitoring detector candidates were then assessed to demonstrate these could be used to verify the stability of the payload.</p> <p>Alignment during ground testing was discovered to be a critical technical risk to the OGSE system. It will be shown how monitoring alignment from ambient to cryogenic temperatures led to a major redesign of the OGSE architecture. Moreover, Ariel’s tiny field of view (~30’’) leads to extreme (arcsecond) alignment maintenance requirements. An alignment monitoring system will be presented, built and verified, to enable the closed-loop monitoring required to keep the OGSE spot within the payloads’ spectrometer slits.</p> |
| spellingShingle | Spry, R Testing the Ariel exoplanet space observatory |
| title | Testing the Ariel exoplanet space observatory |
| title_full | Testing the Ariel exoplanet space observatory |
| title_fullStr | Testing the Ariel exoplanet space observatory |
| title_full_unstemmed | Testing the Ariel exoplanet space observatory |
| title_short | Testing the Ariel exoplanet space observatory |
| title_sort | testing the ariel exoplanet space observatory |
| work_keys_str_mv | AT spryr testingthearielexoplanetspaceobservatory |