XRT Picture of the Week (XPOW)

XRT Home XRT Mission Ops YouTube


2026 May 18

Hinode/XRT Comet MAPS observation pointings

Collage of XRT images obtained at each Comet MAPS pointing. XRT_PREP and dust correction were applied.

Preparing for the Comet MAPS (C/2026 A1) Observation

This article was written for the record of our preparation for and outcome from the Comet MAPS (C/2026 A1) observation scheduled on April 4, 2026. Unfortunately, the comet broke down before reaching its perihelion, the main location of our observation, and thus nothing was detected in the obtained images.

However, the preparation of the observing program took concentrated effort to create multiple complicated observing sequences in a short period of time. It is our desire that this record provides useful information for the next opportunity of comet observation, and that the observing sequences can be prepared more easily with plenty of time.

[A] Prediction of comet location

Predicted helioprojective location of Comet MAPS

Prediction of the Comet MAPS location. Click to enlarge.

[B] Observing plan

HOP 527 (Comet MAPS) was included in the 20260404 timeline prepared by Joy Velasquez (XRTCO of the week at SAO). The pointing information was provided by Wei Liu (HOP527 PI) during the daily meeting on 4/3. 

--- date --- time -------  x / y (arcmin) --------- comment ---------------
2026/04/04 11:27:00   /* -800.0/ -520.0 : # OP start + 10min, HOP 527 #1 */
2026/04/04 13:50:00   /*  840.0/  480.0 : HOP 527 #2 */
2026/04/04 15:04:00   /*  315.0/  404.0 : HOP 527 #3 */
2026/04/04 15:49:00   /* -508.0/ -170.0 : HOP 527 #4 */
2026/04/04 16:20:00   /* -900.0/ -300.0 : HOP 527 #5 */
---------------------------------------------------------------------------
The HOP527 uses three XOBs at five separate pointings:
  • Ingress over the South-East limb
  • Before/after perihelion close to North-West limb
  • On-disk transit 1
  • On-disk transit 2
  • Egress off South-East limb
XRT was requested to take Al-mesh images with 8-sec exposure time. However, in order to avoid risky situations for the CCD and excessive saturation that may cover the comet's orbit, we used a shorter exposure time.

XRT was requested to use a 1024x1536 pixel FOV. However, the orbit of the comet did not appear to fit this rectangular FOV. We modified the FOV to a square shape (1024x1024) to save telemetry.

XRT was requested to keep observing during the SAA passage. Therefore, we needed to remove Bad_Photo entry/exit commands during the comet observations. We also disabled flare control in the sequence so that comet observations would not be disturbed by flares. 

MDP_XRT_FLD_DIS
MDP_XRT_FLRCTRL_DIS
Three new XOBs for HOP 527 were created by Keiji Yoshimura (XRTCO previous week) and tested in the 20260402 timeline. After the test run, some XOBs were modified. Below are their final forms.

XOB#1D47:
  • Intended for use in phase (1) and (5)
  • Almesh 1024x1024 pixels with 2x2 binning (--> 512x512 images)
  • Offset to SE
  • 4 sec exposure
  • 15 sec cadence due to telemetry limit
  • Focus position in the SEQ should be set at -86 (wide-FOV)
XOB#1D45:
  • Intended for use in phase (2)
  • Almesh, mixture of 1x1 and 2x2 binning; both yield 512x512 images
  • Shorter exposure time to avoid saturation from the ARs near the ROI
  • 4 sec exposure, 512x512 pixels with 1x1 binning
  • 1.4 sec exposure, 1024x1024 pixels with 2x2 binning
  • 10 sec cadence
  • Focus position in the SEQ should be set at -361 (narrow-FOV)
XOB#1D48:
  • Intended for use in phase (3) and (4)
  • Almesh, 4x4 CME watch with AEC2
  • 30 sec cadence due to telemetry limit
  • Focus position in the SEQ should be set at -86 (wide-FOV)

[C] Obtained images

Here are movies of the obtained images. Note that they are raw data, before applying XRT_PREP and dust correction.

YouTube overview movie: link The title image above is a collage of images obtained at each pointing. XRT_PREP and dust correction were applied. However, stray light subtraction was not performed, because we do not know the stray light pattern for these particular pointings. The stray light component depends strongly on the satellite pointing, and we mainly measure it at disk center and limb pointings each year.

[D] Some takeaways
  • The actual pointings were determined one day before the OP upload, which did not allow enough time to modify the XOBs.
  • We used a square FOV to save telemetry, but the pointings were determined to optimize EIS's rectangular FOV. As a result, XRT's observing areas, which had been prepared in XOBs on the previous day, were slightly shifted NE-ward from our expectation. Keeping the same FOV shape as EIS may make preparation easier.

[E] Reference: past comet observations by Hinode

Keywords: Flare
Filters: Al_mesh


(Prepared by Aki Takeda & Keiji Yoshimura & Rhiannon Fleming)

The XRT instrument team is comprised of SAO, NASA, JAXA, and NAOJ.

Back Archive Next