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HINODE Operation Plan (HOP)

accepted on

24-oct-2024


 HOP No.

 HOP title

HOP 0496

Comet C/2024 S1 (ATLAS) Observing Campaign on 2024-Oct-28

plan term

2024/10/28-2024/10/28

@ @

proposer

 name : Liu, Brooks, Raymond, Reeves @  e-mail : weiliu[at]lmsal.com

contact person in HINODE team

 name : Reeves/Testa, Warren/Ugarte-Urra @  e-mail : kreeves[at]cfa.harvard.edu, ptesta[at]cfa.harvard.edu, harry.warren[at]nrl.navy.mil,
ignacio.ugarteurra[at]nrl.navy.mil

 abstract of observational proposal
Main Objective: The objective of this HOP is to investigate the coronal response to the intrusion of the comet into the solar corona and to facilitate cross-disciplinary collaboration with night-time astronomers to probe cometary science using solar instruments.

Scientific Justification: Sun-grazing comets are those with perihelion distances of less than a few solar radii (< 3.45 RS from the Sun's center, within the fluid Roche limit, Jones et al. 2018), are of particular science valuable. They offer rare opportunities with two-fold sciences: using such comets to probe the solar corona (solar physics), and to explore cometary science at the same time. The intense solar radiation during their close perihelion passages evaporates thick layers of near-surface material, exposing their otherwise invisible pristine interiors. Their high-speed intrusion into the million-degree magnetized solar corona, in extreme cases skimming or plunging through the solar surface, makes them natural probes of the solar atmosphere inaccessible to human-made instruments (Rast et al. 2021, Solar Physics).

 request to SOT
N/A because this is an off-limb target.

 request to XRT
(following HOP 242):
Field-of-view: 1024x1536 pixels
CCD Center: TBD
Binning: 2
Cadence: 12 sec
Filter: Al-mesh
Exposure: 8 sec, fixed (no AEC)
No flare response (important so that FOV doesn't change)
Do not stop observations for SAAs

Synoptic images (Al-mesh, G-band, and VLS closed G-band), and a dark image with matching FOV, should be taken at the start of the observing period for alignment and calibration.

An XOB has already been created for test purposes (#19DF), but the CO must edit it for use. The Al-mesh exposure time should be changed to 8-sec and the loop count should be increased to ensure that observations don't stop. Otherwise, the existing XOB should be fine but the CO should verify.
(following HOP 242)

 request to EIS
1) Our strategy is to have a combination of slot and slit observations, with the wide slot to maximize the likelihood of capturing the comet and slit rasters/sit-n-stare to obtain spectroscopic diagnostics.

We would like to run the following studies in a sequence:

1.1) 10:37-11:07 UT, on 2024-Oct-28
#91 Alignment_266: sit-and-stare wide slot (266"x512") including He II 256A.

1.2) 11:07-12:27 UT (-40 minutes before perihelion to +40 minutes after, covering 80 minutes)
#557 HPW023_FULLCCD_V3s2 : Sit-and-stare with 2" slit (100s exposures).
~20 minutes duration for each pointing, to be optimized after considering slew time from one pointing to
another
(The 20 duration is based on the lifetime of bright tail striations of Comet Lovejoy)

1.3) 12:27-13:47
#403 Atlas_30 or #404 Atlas_60 raster scan: 30-60 min full CCD spectra with 2" slit (60"x160").

2) The exact pointing and timing will be communicated to the CO by the proposers before the Hinode draft plan is built.

3) There are a number of spectral lines of interest:
Oxygen lines (from cometary water ice among other volatile material):
O VI (171 A), O V (193), O III (263), and O IV (279).
Fe VIII, Fe IX, Si VII, and Si VIII may also be observable.
Ne III line at 251.14A: would be interesting, as it could potentially be the first confirmed detection,
relevant to cometary formation models.

 other participating instruments
IRIS:
Special OBS (4204700123) built in August 2020 for comet observations.

Additional instrument coordination:
Currently we have SDO, Solar Orbiter, Proba-2, IRIS, among other missios, plus some potential ground-based facilities in Europe participating in this campaign.

 remarks
Dates: A new sungrazing comet named C/2024 S1 (ATLAS) is predicted to arrive at its perihelion on 2024-Oct-28 (~11:47 UT viewed from Earth/Hinode) at an altitude of ~0.7 R_Sun above the northeast solar limb.

Time window: 1-2 hours before to 2 hours after perihelion, a total duration of 3-4 hours.

Target(s) of interest: The perihelion timing as seen at Hinode, corrected for light travel time is: 2024-10-28T11:47 at helioprojective coordinates of (x,y)= (-1162", 1066")
The predicted comet orbit coordinates are maintained and updated at, e.g., taking into Hinode orbital position:
http://sprg.ssl.berkeley.edu/~shilaire/Comets/20241028_ATLAS/20241021_elements/Hinode.png
http://sprg.ssl.berkeley.edu/~shilaire/Comets/20241028_ATLAS/20241021_elements/Hinode.txt

Previous HOPs:
HOP 269. Berger, Hillier, Liu 2017 ApJ (https://ui.adsabs.harvard.edu/abs/2017ApJ...850...60B)

Additional remarks:
I'm sorry for submitting this late, but the comet was recently discovered and the observing campaign just got underway. We hope this can still be discussed and approved at the Hinode monthly meeting on Oct 23.

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