Data Acquisition

Data Flowchart

The VAMPIRES cameras operate predominantly through scexao5, however the network architecture is slightly more complicated

scexao5 serves as the main entrypoint for controlling the camera processes (the camstart scripts and tmux sessions) as well as the computer the data is initially saved to. Contrarily, the pupil camera is plugged directly into sonne over USB.

Once the shared memory streams for vcam1 and vcam2 are running on scexao5 they will be transmitted over the network in two ways

1. 20 Gbps TCP link (fast)

2. 500 Mbps ZMQ link (slow)

The TCP links are able to transmit the full-speed data streams from scexao5 to scexao6 so that any code running on scexao6 can operate in real-time. The ZMQ links are throttled to 20 FPS to conserve some network bandwidth- these are only appropriate for simple control scripts (like autofocus) or for camera viewers.

Logging FITS files

To log FITS files with full headers, you will need to set up a milk-streamFITSlog process on scexao5. The recommended interface is to call

sonne $ vampires_preplog

this will launch an interactive process to set up logging for the VAMPIRES cameras.

Warning: File size

Be careful to not save too many frames to each data cube– when individual data cube sizes grow too large simple tasks (loading into DS9 or as a numpy array) become annoyingly slow. This is exacerbated in multiband imaging mode, which produces 280 MB/s per camera. We aim for file sizes around 1-2 GB, max, which corresponds to the following cube lengths

Crop	Max. frames	File size
STANDARD	2000	1.1 GB
MBI	250	1.2 GB
MBI_REDUCED	500	1.2 GB

Once this process is finished, you should launch an FPS control from scexao5

scexao5 $ FPS_FILTSTRING_NAME="streamFITSlog-vcam" milk-fpsCTRL

you should see one or two processes, depending on how many cameras you’re logging. The left three numbers should all be green. If the right of those three numbers is gray, press SHIFT + R over the process to start it.

Option 1: Using VAMPIRES scripts

If you are using both cameras, you’ll want to using scripts that psuedo-simulatneously trigger both cameras’ logger processes. This is enabled with the following VAMPIRES scripts:

• vampires_startlog

• vampires_pauselog

• vampires_pauselog --wait

• vampires_stoplog

• vampires_stoplog --kill

Option 2: Directly using fpsCTRL

If you are only logging one camera it is usually simple enough to initiate camera acquisition directly through fpsCTRL. To initiate logging, press the right arrow to go into the camera’s logger process and then arrow down to the saveON option. The space bar will enable and disable the process. If a FITS cube has not been filled when saveON is disabled the file will be truncated; to finish the last cube arrow down and enable the lastCubeON option, instead.

If you change camera crops or if you want to change the number of frames per cube, you will need to restart the logger process. This is because the data buffer used for the FITS file needs to be reallocated when the memory footprint changes. To restart the process, go back to the main fpsCTRL menu and do CTRL+R, then adjust the cube size, then go back and SHIFT+R the process.

Watching FITS files

To confirm each FITS file gets written appropriately, there is a tool which watches directories for new FITS files and shows a quick file summary. To run this script, call fitswatcher with a glob over the directories to watch–

scexao5 $ fitswatcher -n 3 <dir>/vcam*

the -n flag will show the specified number of files per folder in the TUI, by default 2.

Tip: Tonight’s folder

If you are logging data to gen2 for nightly observing, the following one-liner should work to set up fitswatcher for VAMPIRES

scexao5 $ fitswatcher -n 3 /mnt/fuuu/ARCHIVED_DATA/$(date -u +'%Y%m%d')/vcam*

╭─ FITS Watcher - 2024-06-13T00:11:20.347365 ────────────────────────────────╮
│ /mnt/fuuu/20240611/vcam1/ - 8 FITS files (29 GB)                           │
│   vcam1_00:00:03.628172287.fits - (1000, 1104, 2228) 4919 MB | DARK scexao │
│   vcam1_23:59:49.294402958.fits - (249, 1104, 2228) 1225 MB | DARK scexao  │
│   vcam1_23:59:34.528434921.fits - (611, 1104, 2228) 3006 MB | DARK scexao  │
│                                                                            │
│ /mnt/fuuu/20240611/vcam2/ - 7 FITS files (29 GB)                           │
│   vcam2_00:00:05.715949178.fits - (1000, 1104, 2232) 4928 MB | DARK scexao │
│   vcam2_23:59:56.721432449.fits - (248, 1104, 2232) 1222 MB | DARK scexao  │
│   vcam2_23:59:35.200653725.fits - (581, 1104, 2232) 2863 MB | DARK scexao  │
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