title: Preparing for the Comet MAPS (C/2026 A1) Observation authors: Aki Takeda, Keiji Yoshimura and Rhiannon Fleming filter: Almesh This article was written for the record of our preparation for and outcome from the Comet MAPS (C/2026 A1) observation scheduled on April the 4th, 2026. Unfortunately, the comet broke down before reaching at its perihelion, the main location of our observation, and thus nothing was detected in our 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 the observing sequences are prepared more easily in plenty of time. [A] prediction of comet location. (link to "C2026_A1_MAPS_HelioProj.png") [B] observing plan: HOP 527 (Comet MAPS) was included in the ["20260404 timeline" make a link to "./xrt_plan_20260404.pdf"] 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 3 XOBs at the 5 separate pointings as follows. (1) ingress over the South-East limb (2) before/after perihelion close to North-West limb (3) on-disk transit 1 (4) on-disk transit 2 (5) egress off South-East limb. XRT was requested to take Al-mesh images with 8-sec exposure time. However, in order to avoid the risky situations of the CCD and excessive saturation which may cover the comet's orbit, we will use a shorter exposure time. XRT was requested to use 1024x1536 pixel FOV. However, the orbit of the comet does not look to fit this rectangular FOV. We modified the FOV to a square shape (1024x1024) to save the telemetry. XRT was requested to keep observing in the SAA passage. Therefore, we should remove Bad_Photo entry/exit commands during the comet observations. Also, we should disable flare control in the sequence, so that comet observations are not disturbed by flares. MDP_XRT_FLD_DIS MDP_XRT_FLRCTRL_DIS Three new XOBs for the HOP 527 was 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 form. XOB#1D47: + intended for use in phase (1) and (5) + Almesh 1024x1024 pixels with 2x2 binning (--> 512x512 images) + offset to SE + 4sec exposure + 15sec 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 yields 512x512 images) + even shorter exposure time to avoid the saturation from the ARs near the ROI + 4sec exposure, 512x512 pixels with 1x1 binning + 1.4sec exposure, 1024x1024 pixels for 2x2 binning + 10sec 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 + 30sec cadence (due to telemetry limit) + Focus position in the SEQ should be set at -86 (wide-FOV). [C] obtained images: Here are movies of obtained images. Note that they are raw data, i.e., before applying XRT_PREP and dust correction. * ["Pointing #1 movie" make a link to "./comet_pt1.mp4"] * ["Pointing #2 movie" make a link to "./comet_pt2.mp4"] * ["Pointing #3 and #4 movie" make a link to "./comet_pt3_pt4.mp4"] * ["Pointing #5 movie" make a link to "./comet_pt5.mp4"] The title image in the above is a collage of images obtained at each pointing. The XRT_PREP and dust correction were applied. However, the stray light subtraction was not performed, because we do not know the stray light pattern for these particular pointings: The stray light component highly depends on the satellite pointing and we mainly measure at the disk center and each limb pointings every year. [D] some takeaways: * The actual pointings were determined one day before the OP upload, that did not allow us 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 the result, XRT's observing areas (prepared in XOBs, on the previous day) were slightly shifted (NE-ward) from our expectation. Maybe keeping the same FOV shape as EIS makes the preparation easier. [5] reference: past comet observations by Hinode * 2011/12/15 Comet Lovejoy in ["20111215 timeline" make a link to "https://xrt.cfa.harvard.edu/missionops/timelines/20111215_Plan/xrt_plan_20111215.pdf"] with XOB#18C9 and #18CA (no HOP). * 2013/11/28 Comet ISON as ["HOP 242" make a link to "https://www.isas.jaxa.jp/home/solar/hinode_op/hop.php?hop=0242"] * 2024/10/28 Comet ATLAS as ["HOP 496" make a link to "https://www.isas.jaxa.jp/home/solar/hinode_op/hop.php?hop=0496"]