Band-limited integrated scatter measurements on super polished optical mirrors

Venkata, Suresh; Budihal, Raghavendra Prasad; Venkatasubramanian, Natarajan; Padavu, Umesh Kamath; Sriraman, Kathiravan

doi:10.1117/1.oe.59.8.084106

Cited by 9 publications

(3 citation statements)

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Section: Optical Design Of Velcmentioning

confidence: 99%

“…Detailed studies (theoretical and experimental) are carried out to derive the fabrication specifications of the M1 and to define the limits of particulate and molecular contamination over M1 surface. [5][6][7][8][9] 2.1 Performance Specifications of VELC Based on the optical design, performance, thermal, and tolerance analysis, achievable performance of the instrument is determined. Expected performance of VELC in different channels is given in Table 1.…”

Section: Optical Design Of Velcmentioning

confidence: 99%

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Ground calibration of visible emission line coronagraph on board Aditya-L1 mission

Budihal,

Narra,

Venkatasubramanyam

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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Visible emission line coronagraph (VELC) is the prime payload on board India's first space solar observatory Aditya-L1. VELC is a unique payload with simultaneous observational capabilities in imaging, spectroscopy, and spectro polarimetry modes. VELC is capable of achieving high spatial, spectral, and temporal resolution closer to the solar limb 1.05 R ⊙ compared to the existing space and ground-based solar coronagraphs. VELC consists of a total of 44 optical elements in 18 groups, which are custom designed and developed to meet the desired performance requirements. In addition, it consists of four mechanisms out of which two are multioperational with expected life cycle of million operations. Four detectors (three sCMOS and one InGaAs) are used to record the data. The performance of the payload depends on the performance of individual element, subsystems, and the system level performance of all the elements (such as optics, mechanism, and detectors) together. To ensure the desired performance levels are achieved, each element/subsystem should be tested prior to integrating them together. Evaluation of performance of the integrated system is essential to validate the payload capabilities to meet the proposed science goals. This paper summarizes the calibration tests carried out on the integrated system and compares the results obtained with respect to the design requirements to meet the proposed science goals.

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Section: Optical Design Of Velcmentioning

confidence: 99%

Section: Optical Design Of Velcmentioning

confidence: 99%

Ground calibration of visible emission line coronagraph on board Aditya-L1 mission

Budihal,

Narra,

Venkatasubramanyam

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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“…The angle resolved scatter from M1 is measured using the custom build near specular scatterometer (NSS). 11 Minor design modifications are done in the NSS to accommodate and measure the ARS from M1, as shown in Fig. 6.…”

Section: Angle Resolved Scatter (Ars) Measurements On Primary Mirror ...mentioning

confidence: 99%

Optical metrology on primary mirror of visible emission line coronagraph on board Aditya-L1 mission

Venkata

Singh

Venkatasubramanian

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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The visible emission line coronagraph (VELC) on board the Aditya-L1 mission is an internally occulted reflective coronagraph. It is capable of simultaneous observations of the solar corona in imaging, spectroscopic, and spectropolarimetric modes very close to the solar limb, to 1.05 R ⊙ (R ⊙solar radius). Primary mirror (M1) of the VELC receives the light from both the solar disk and the corona up to 3 R ⊙ . In the VELC, occultation happens at the focus of the M1. Secondary mirror (M2) with a central hole size equal to 1.05 R ⊙ is mounted at the focal plane of M1 and serves the purpose of an internal occulter. To meet the proposed science goals of the payload, M1 surface should be super polished with good imaging characteristics. This results in stringent requirements of the surface figure and microroughness on the mirror surface. M1 is an off-axis parabola, so achieving the demanding requirements is quite challenging. At the same time, testing of M1 after development is crucial for evaluating its performance. This paper provides the details of the optical metrology tests carried out on M1 along with the results obtained and their implications on the performance of the VELC.

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Scatter due to Ultraviolet (UV) photopolymerization of molecular contamination on optical surfaces

et al. 2020

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Band-limited integrated scatter measurements on super polished optical mirrors

Cited by 9 publications

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Ground calibration of visible emission line coronagraph on board Aditya-L1 mission

Ground calibration of visible emission line coronagraph on board Aditya-L1 mission

Optical metrology on primary mirror of visible emission line coronagraph on board Aditya-L1 mission

Scatter due to Ultraviolet (UV) photopolymerization of molecular contamination on optical surfaces

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