SXT support of SOHO JOP 080

(This is only a rudimentary page to show target locations and representative images. Don't expect much in the way of analysis.)

15-May-98 update

Summary of SXT observations: From 17:22:18 to 17:57:42 we have full-resolution (2.45 arcsec pixels) images in AlMg filter. The field of view is 5.2 arcmin square; the images were made at a cadence of one every eight seconds. There are 21 dark frames at regular intervals throughout the sequence; at nearly the last minute we decided to put in a handful of thin aluminum-filter images as well, to allow low-cadence temperature measurements. As a result, we ended up with 22 Al.1 images at regular intervals throughout the sequence.

From 17:58:46 to 18:02:14, Yohkoh was in the South Atlantic Anomaly; in this region we run at a lower bitrate, and the images in this short interval are only half-resolution.

The period 17:22 to 18:02 represents the maximum that Yohkoh's memory can hold. Once the memory was full, we stopped recording images, in order to avoid overwriting the first part of the run.

Images can be viewed at URL:

An IDL-save file is available. Email McKenzie to find out how to get it.

13-May-98 entry

The JOP coordinators have tentatively chosen AR 8218 as the target for our high-cadence observations; it's the large boxed region near the center of the southern hemisphere in the image below. SXT is capable of making images of this region with a 16-second cadence. However, since there is a fair chance that this region will produce sizeable flares in the next several hours, we may make an eleventh-hour change of target.

Watch this space for updates.

12-May-98 entry

SXT will upload the table with the JOP observations at 17:07 UT on 13-May (Pass 3 Thursday morning). The table will be replaced at the next KSC pass, 18:50 UT; this will effectively end the SXT portion of the JOP. Between approximately 17:20 UT and 17:59 UT, SXT will make full-resolution images (cadence not yet determined). At 17:59 Yohkoh enters the South Atlantic Anomaly region, and does not leave SAA until 18:21 UT. During this time SXT will make half-resolution images. Between 18:21 and 18:27 Yohkoh will be in daylight and out of the SAA, and SXT will make full-resolution images.

The target for this JOP is not yet determined. Some possibilities are shown in the image below (click to see a larger image). Judging from the brightnesses of these regions on 11-may at 21:43 UT, all these regions can be imaged with a 16-second cadence. If the observing region is cut in half, the images can be made at twice the cadence.

The southernmost region, marked with an asterisk, is too faint to provide full pixel wells at 16-second cadence. However the brightest portions of the target will provide pixels that are about 70% full.

David E. McKenzie