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HMI Focus Adjustments Today, Data may be Unavailable

17 Oct 2018, 00:17 UTC
HMI Focus Adjustments Today, Data may be Unavailable
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Anything looking at the Sun tends to heat up. The SDO instruments have been looking at the Sun for 8.5 years. Although they are designed to look at the Sun for a long time, some changes still happen. For example, the coatings on the HMI instrument housings and optical surfaces have been degrading slowly but steadily, causing the instrument to absorb more solar radiation and heat up. The front surface of HMI’s telescope is now hot enough that the HMI team is having difficulty maintaining proper focus. Without some adjustments, this problem will only get worse as the instrument continues to age. For this reason, the HMI team is going to increase the operating temperatures of the front of the telescope and adjust the internal focus mechanism. This should give the instrument many more years of precise control and excellent data. The process of increasing the operating temperatures is a slow one — the team will begin heating the front telescope tube up at 1000 UTC on Tuesday, October 16, and will then wait six hours for the temperature to stabilize. The next step is to fine-tune the temperatures. These smaller changes will need about an hour for the temperature ...

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