LIRIC

LIRIC under development in lab (covers removed). ©2023 A.Piascik

Introduction

The Liverpool Infra-Red Imaging Camera is an instrument development project co-funded by STFC and LJMU. It was designed and built by the ARI and will be available from 2024 Q1, replacing the now-decommissioned IO:I camera. It offers rapid X and Y axis fixed-distance offsetting (nodding) for sky background subtraction.

Status

2024 Q1:
Installed on-mount and available for raw observation. Pipeline in development

Specifications & Performance

Data is for detector temperature = -20°C

Filter Set

LIRIC has an uncooled 5-position filter wheel.
Currently a J-band and a FELH1500 low pass filter are installed.
The Johnson Bessell R-band filter is no longer availble.
The FELH1500 filter and sCMOS detector response combine for a pseudo H-band.

Dithering

Dithering is achieved by two cams to mechanical offset the camera X and Y positions within the image plane.
The camera position cycles through each offset in sequence for each exposure, up to the number of positions requested.
Movement between positions is in the order 1-9 and takes between 2-4 seconds to change to a new position.

The base exposure time at each offset position is set in the configuration to 100ms or 1000ms.
The actual exposure time at a position is the sum of co-added base exposures times.
Read-out time is negligible.

When scheduling an observing run, the camera movement can be set to either small or large offsets, but not both

Phase II Options

Instrument Config - Create New Instrument Config

Detector Config - Binning
1x1 only available

Filter Specification - Filter Wheel 1
FELH1500 - pseudo H-band filter
Barr-J

Nudgematic - Offset Size
Sets the linear offsets from the centre position
None - No offset, camera will not move
Small - 20 arcsec linear offsets
Large - 60 arcsec linear offsets

Co-add - Exposure Length
Base exposure time used for co-adding images to produce a FITS file for a position
100ms
1000ms

Exposure Dialog Box

Exposure
Mult-run button must be selected

repeats
The number of offset positions the camera will move to
Offset positions are visited in the order, 1-9
Positions are omitted if repeats < 9, or revisited if repeats > 9

Exposure Time
The total exposure in seconds for a single visit to an position
It must be a multiple of Co-add - Exposure Length

Bias and Darks

The LIRIC uses a sCMOS detector and does not have a shutter.
IR observations normally take several offset images and use sky-subtraction to remove bias and dark currents.

For single exposures prepared bias or dark frames are provided below.
Bias frame exposure time is 20µs, dark frame exposure is either 100ms or 1s
For dark frames a gold mirror target is automatically selected as the filter.