Optical configuration and optical tests of the HartRAO Lunar Laser Ranger

Nkosi, Nokwazi Purity.; Combrinck, W. L.; Akombelwa, Mulemwa

doi:10.2113/gssajg.119.1.99

Cited by 2 publications

(3 citation statements)

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“…A difference is noted in the slightly higher standard deviation (hereafter denoted as SD) in respect of the relative displacements at Prism 2. As such, as shown in Nkosi et al (2016), gravity-induced deformation on the lower arc of the tube front may have had an effect.…”

Section: Analysis Of Relative Displacements Of the Llr Tubementioning

confidence: 83%

“…This finding could be an indication of an area on the tube that is subject to greater structural deformation. Considering the location of Prism 2 at the lower arc of the tube front, this finding suggests that as opposed to other areas on the tube front, there could be a combination of thermally-induced (Tsela et al, 2016a) and gravityinduced (Nkosi et al, 2016) deformations occurring concurrently on the tube, thus leading to increased variability. This increased variability is hypothesised to introduce more elevationpointing offsets than azimuth for the LLR, as it has been shown in other studies that there are strong correlations between ambient temperatures and elevation-pointing offsets, reaching about 10″ during telescope pointing (Mittag et al, 2008).…”

Section: Analysis Of Relative Displacements Of the Llr Tubementioning

confidence: 95%

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Analysis of thermally-induced displacements of the HartRAO Lunar Laser Ranger optical tube: impact on pointing

Tsele,

Combrinck,

Botha

et al. 2023

SA J of Geomatics

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The Hartebeesthoek Radio Astronomy Observatory (HartRAO) of South Africa is developing a Lunar Laser Ranging (LLR) system to achieve sub-centimetre range precision to the Moon. Key to this high precision expectation, which includes improving the overall operational performance of its telescope, is the thermal analysis of the telescope structure. In this study, thermal sensors were mounted on the thermally- important areas of the tube structure to measure the tube displacements emanating from the varying ambient air temperatures. A laser distance-measurement system was used for this purpose. Results showed that while the optical tube undergoes structural changes with changes in temperature, the tube position closer to the place where the spider assembly is mounted is unevenly displaced in three directions. In particular, for the time period considered in this study, it was found that the relative displacements on average at prisms 1, 2 and 3 in the vertical direction were 2.5540 ± 0.0007 m, 1.3750 ± 0.0008 m and 1.9780 ± 0.0007 m, respectively. The corresponding standard deviation (SD) values of ±0.0007 m, ±0.0008 m and ±0.0007 m denotes the average deviations that occurred in the vertical direction at the centre of prisms 1, 2 and 3, respectively. The generally higher SD of relative displacements in the vertical direction rather than in the easting and northing directions, suggest that the tube experienced greater variations in the vertical direction. Furthermore, the lower arc of the tube front, was found to have increased variability, and therefore it was hypothesised to introduce more elevation pointing offsets than azimuth for the LLR. This information constitutes an important input for guiding the efforts to determine the extent of the correction needed to be fed into the LLR telescope pointing model to counteract expected thermally induced pointing offsets.

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Section: Analysis Of Relative Displacements Of the Llr Tubementioning

confidence: 83%

Section: Analysis Of Relative Displacements Of the Llr Tubementioning

confidence: 95%

Analysis of thermally-induced displacements of the HartRAO Lunar Laser Ranger optical tube: impact on pointing

Tsele,

Combrinck,

Botha

et al. 2023

SA J of Geomatics

View full text Add to dashboard Cite

show abstract

“…Additionally, gravity and wind are additional factors that require development of analytical models to investigate their induced relative effects on the pointing performance of the LLR optical telescope. The models, particularly on gravity-induced deformations of the telescope primary mirror are being studied in collaboration with other research teams at HartRAO (Nkosi et al, 2016).…”

Section: Resultsmentioning

confidence: 99%