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Fig 1.   Comparison of the Telescope Targets acquired in S1282 session and the Telescope Slew Paths Drawn.
There are clearly several targets for which the corresponding telescope slew path hasn't been drawn.
Issue was identified to be due to a bug that was recently introduced after session S1279. Bug has now been fixed.

GRB alerts that the Observatory can respond to are fairly rare (the Observatory has to be operating / running at the time and the GRB target has to be above the horizontal at a position that telescope is permitted to slew to, and the positional error of GRB has to be smaller enough that telescope's camera FOV will be able to image the target).

Given the desire to image the location of a GRB Alert as soon as possible after the Alert is raised, it is appropriate to understand the Observatory's response to the alert and determine if there is anything that can be done to shorten the time between the receiving the alert notice and taking the first image.

The AstroVOE program running on the Observatory Computer monitors the GCN Network 24x7.

The first GCN/Swift Notice concerning Swift Trigger 1274039 was seen by AstroVOE at 02:19:17. At this point it wasn't clear if the trigger was deemed to be due to a GRB so as per design no action was taken.

NOTICE_DATE: 2024-12-13T02:19:15
ROLE: Observation
NOTICE_TYPE: Swift-BAT Quicklook Position
PACKET_TYPE: 97
TRIGGER_NUM: 1274039, Ser Num: 1

This was followed 2s later by a Swift-BAT GRB Position notice for a Burst Event that had occurred at 02:19:00.14 UT

TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: 2024-12-13T02:19:17
ROLE: Observation
NOTICE_TYPE: Swift-BAT GRB Position
PACKET_TYPE: 61
TRIGGER_NUM: 1274039, Ser Num: 3
GRB IDENTIFIED: YES
CONSTELLATION: Lynx (Lyn)
GRB RA: 07 44 35.496 [J2000]
GRB DEC: +35 16 49.44 [J2000]
ERROR_RADIUS: 3.0 [arc min]
COORD_SYSTEM: UTC-FK5-GEO
EVENT_INTENSITY: []
BURST_TJD/SOD: 20657 [days], 8340.14 [sec]
BURST_DATE: 2024-12-13 (Fri)
BURST_TIME: 02:19:00.14 UT
BURST_INTENSITY: 7587 [cts]
BURST_PEAK: 985 [cts]
BKG_INTENSITY: 16000 [cts]
BKG_DURATION: 8 [sec]
RATE_SIGNIF: 127.59 [sigma]
IMAGE_SIGNIF: 20.83 [sigma]
TRIGGER_INDEX: 147
IMPORTANCE: 0.90
INFERENCE PROB.: 0.90
CONCEPT: process.variation.burst;em.gamma
COMMENT: Swift Satellite, BAT Instrument
IVORN: ivo://nasa.gsfc.gcn/SWIFT#BAT_GRB_Pos_1274039-476
PACKET_NAME: SWIFT_BAT_GRB_POSITION

As this was identifiable as a GRB Alert the AstroVOE reacted to the GCN Message and quickly made a target assessment to see if the Observatory could react.  The GRB lay in the constellation of Lynx which was well positioned in the sky at the time, and the error radius of only 3 arc min was small enough for imaging with the 12" telescope and ST-10 Camera.

- AZIMUTH: 175.89 [deg]
- ALTITUDE: 67.80 [deg]
- MOON DISTANCE: 61.02 [deg]
- MOON ILLUMINATION: 93.13 [%]
- NEAR BRIGHT STAR: NO
- CAN REACT?: YES

It concluded that the Observatory could react and as a result the GRB target was entered into the Targets Database and flagged as Priority 1 ToO, which led to AstroMain aborting the existing target and immediately slewing the telescope to the GRB's coordinates in order to take a series of images.

The following AllSky Picture shows the position of the GRB Target (yellow) and the position of the scope at the time that alert was received (yellow). The image shows bright moonlit sky (moon 93% phase) and some passing cloud (fortunately this didn't effect the observation of the GRB target). The required slew was relatively small, just 22.6°, and took only 31s.

Swift Trigger 1274039 (GRB 241213A)
Location
- RA (J2000) 07 44 41.17
- Dec (J2000) +35 16 46.3
- Error (90% conf)  1.9"

Final Location
RA (J2000): 07h 44m 41.13s
Dec (J2000): +35° 16' 44.6''
90% Error radius: 2''

GRB RA: 07 44 35.496 [J2000]
GRB DEC: +35 16 49.44 [J2000]

https://www.swift.ac.uk/sper/1274039/

Time Line
 

Time		Time from GRB T+mm:ss	Time from GRB Notice T+mm:ss	Event/Activity		Task Time (s)	Notes
02:19:00		T0	T-00:17	GRB Event			GRB Event
02:19:15		T+00:15	T-00:02	Swift-BAT Quicklook Position (1274039)			Swift Quicklook Position 15s after GRB Burst
02:19:17		T+00:17	T0	Swift-BAT GRB Position (1274039)			Swift GRB Position Notice, 17s after GRB Burst
02:19:19		T+00:19	T+00:02	AstroVOE program sees Swift GRB Notice			Notice Received 2s later, 19s after GRB Event
02:19:20			T+00:03	AstroMain ReceivedToO Request		1s	Priority 1 Target Of Opportunity - FastReactMode
02:19:20			T+00:03	Called CCDCamera.Abort		1s	Aborting prior target was very quick.
02:19:21			T+00:04	Stop PHD2 Guiding - Stopping PHD2 Capture & Guiding
02:19:22			T+00:05	Stop PHD2 Guiding - Fail | PHD2 App Status : Guiding		2s	1.5s - 2s wasted.
02:19:23			T+00:06	Save GuideFrameImage			This step could be skipped to save 1.5-2s
02:19:23			T+00:06	Run ConvertFitsToJpg (Guide03_F2)
02:19:24			T+00:07	Stop PHD2 Guiding Info | Guiding already stopped		1s
02:19:24			T+00:07	Begin GRB Swift 1274039 Target
02:19:25			T+00:08	Began slew to GRB Coordinates		31s slew	Slew began 8s after Swift's GRB Position Notice
02:19:56			T+00:39	Begin Locate Frame 1
02:19:57		T+00:57	T+00:40	Take 5s image (locate frame)		5s image	57s after GRB Burst
02:20:07			T+00:50	Begin image link (plate solution)
02:20:12			T+00:55	Finished image link (pointing error 1.3')
02:20:13			T+00:56	Begin Centering Jogs			Small error, jogs could be skipped to save 14s ?
02:20:27		T+01:27	T+01:10	Finished Centering Jogs		14s jogs	Telescope centered 1m 27s after GRB Burst.
02:20:34			T+01:17	Send Guide Request to PHD2
02:21:17			T+02:00	Timed-out waiting of guider to settle after 43.1s		43s guide setup	Can probably begin imaging without waiting for guider to settle or timeout.
02:21:17			T+02:00	Enter TakeMainScopeFrames() routine			2 minutes after Swift's GRB Position Notice
02:21:19		T+02:19	T+02:02	Take 1st exposure (30s)		30s image	2m 19s after GRB Burst.
02:21:53		T+02:53	T+02:36	Finished 1st exposure
02:21:54		T+02:54	T+02:37	Begin Image Link
02:22:01		T+03:01	T+02:44	Finished Image Link (pointing error 0.21')		6s linking	Could be skipped ?
02:22:03		T+03:03	T+02:46	Take 2nd exposure (30s)		30s image
02:22:37		T+03:37	T+03:20	Finished 2nd exposure
02:22:38		T+03:38	T+03:21	Take 3nd exposure (30s)		30s image
02:23:15		T+04:15	T+03:58	Finish 3 x 30s images
02:23:16		T+04:16	T+03:59	Take 5 x 60s images		5 x 60s
02:29:04		T+10:00	T+09:47	Finish 5 x 60s images
02:29:06		T+10:06	T+09:49	Take 5 x 180s		5 x 180s
02:45:34		T+26:34	T+26:17	Finish 5 x 180s

GRB Swift 1274039 - Realtime Images

Locate Frame 5s Image Linked (Plate Solved) Locate Frame The telescope positional error after slew was 1.3' Yellow cross-hairs is the GRB Position from the Swift-BAT GRB Position Notice with a 3' error radius (blue circle). The white cross-hairs is the image centre

1st Main Frame - 30s GRB Position from Swift-BAT GRB Position Notice is now centered in FOV The white cross-hairs shows the final XRT position of the GRB which was only available later

4th Main Frame - 60s

9th Main Frame - 180s

After reduction and post-session analysis final images of the target are shown here.

Assessment was that the imaging had successfully made an immediate post-GRB optical observation, but no optical counterpart was visible. The non-detection limiting magnitude was +19.3,  so any optical counterpart (if any) must be dimmer than this value.

GRB Swift 1274039 - Realtime Image (02:21:20) Blue circle is a 3' confidence radius centred on the Swift BAT Alert Coordinates for 1274039 White Cross-Hairs shows the final XRT position of the GRB

Annotated Raw CCD Image (70% size, linear scale) 30s exposure (single frame), 3x3 binning, Clear Filter 2024-12-13 02:21:20 UT (#1282031) 12" LX200R (at f/10.4) + ST-10XME Auto-guided using TS 80mm APO, ZWO ASI178MC & PHD2

Final 3 x 30s Image Position of GRB (not visible) is shown by black cross-hairs Non-Detection Limiting Magnitude +18.5 (Clear Filter)

Negative CCD Image (150% size, square root scale, cropped 3 x 30s exposure (average combine), 3x3 binning, Clear Filter 2024-12-13 02:22 UT (#1282031-33) 12" LX200R (at f/10.4) + ST-10XME Auto-guided using TS 80mm APO, ZWO ASI178MC & PHD2

Final 3 x 180s Image Position of GRB (not visible) is shown by black cross-hairs Non-Detection Limiting Magnitude +19.3 (Clear Filter)

Negative CCD Image (150% size, square root scale, cropped 5 x 180s exposure (average combine), 3x3 binning, Clear Filter 2024-12-13 02:38 UT (#1282039-43) 12" LX200R (at f/10.4) + ST-10XME Auto-guided using TS 80mm APO, ZWO ASI178MC & PHD2

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