Weekly Notes from the Yohkoh Soft X-Ray Telescope

(Week 5, 1998)

31-Jan-98 03:00 UT

Instrument Status

The Soft X-ray Telescope continues to work without problems. Solar activity was low, and the main excitement of the week was the successful XDT rocket launch (04:30 UT, 31-Jan-98), which is the subject of the weekly science discussion below. Please see the SOHO/XDT coordination page for more details, including lots of SOHO data.

In the display above (click to enlarge), the colored lines show the times of SXT images that currently are on-line at ISAS. The purple lines are flare mode. Alas, the scale is too compressed here to be able to see individual data! Most of the gaps will be filled in when the NASA telemetry arrives. A more detailed report of this week's activities is available here. For a summary index listing of the weekly science reports, click here.

Observation of the week: the XDT rocket

The XDT rocket consists of an innovative normal-incidence X-ray telescope with complementary narrow passbands in the red and blue wings of an Fe XIV emission line. Its difference images will show the coronal velocity field in the line of sight, and in principle feature-tracking in its sum images will show the velocity field perpendicular to the line of sight. The rocket payload was designed and built by an NAOJ/ISAS group led by S. Tsuneta. From the SXT perspective, its success has been an important step scientifically and perhaps as a guide to SOLAR-B instrumentation development. Rocket pointing

Pointing plan for Yohkoh at launch minus 24 hours

The PFI's were set N of AR8146 as shown, using fixed pointing at the position predicted for 04:30 UT Jan. 31 (click on the image to enlarge it):

ORIGINAL COORDINATES : 29-JAN-98 21:23:11 ROI center (image coords): x = 292 y = 382 OR Coordinates : NS = 191 EW = 109 Heliographic Coordinates : N 19.7 W 7.3

ROTATED COORDINATES : 31-JAN-98 04:30:00 Rotated OR Coordinates : NS = 190 EW = 80 Heliographic Coordinates : N 19.7 W 25.5

Actual Yohkoh pointing

These are actual AlMg images (alternating between 1.88 s and 3.78 s nominal exposure times) obtained by Yohkoh just after the flight, covering the time range 04:41:27 to 04:47:39 UT;

These are the corresponding Al12 images, all at the limiting exposure of 7.55 sec, over the range 04:40:45 to 04:46:57 UT.

The preliminary heliographic coordinates of the center of these images are (N20.9, W20.7); the SXT images are 128x128 pixels and the pixel size is 2.455 arc sec.

HSH, 30-Jan-97 04:30 UT (email hudson@isass0.solar.isas.ac.jp)