FGC/NIRISS (Fine Guidance Sensor/Near Infrared Imager and Slitless Spectrograph), Canadian contribution
Precision pointing for high-quality imaging and slitless spectroscopy
During this test, the ISIM is supporting the Mid-InfraRed Instument (MIRI) and the Fine Guidance Sensor / Near InfraRed Imager and
Slitless Spectrograph (FGS/NIRISS).
He attempted some spectroscopic observations, but his telescope didn't have sufficient light grasp to show anything definitively: 'With the Hilger spectroscope (
slitless) the spectrum was very dim; but there was a bright condensation, possibly in the green.
The writer's instrument is a moving source
slitless Foucault type tester that has undergone many modifications over time.
Regardless, small spectrographs can be characterized as "
slitless" systems with the collimation of the beam at the grating being determined by the internal diameter of the collection fiber or bundle rather than by the entrance slit of the monochromator.
Simple
slitless spectrographs reach less than 1,000 and are therefore considered to be low-resolution instruments.
First the Integrated Science Instrument Module (ISIM) structure laden with the Mid-Infrared Instrument (MIRI) and Fine Guidance Sensor/Near InfraRed Imager and
Slitless Spectrograh (FGS/NIRISS) is lifted onto a test fixture.
The spectroscopic work mentioned above can be done with an inexpensive,
slitless spectrograph.
This means the instrument can do long-slit or
slitless spectroscopy of fields nearly an arcminute square.