GrIm - Users Information

Contact Webmaster for web page errors, corrections, ommisions, and/or additions.

This page last updated: June 28, 2006 - JMD
This page last checked: October 26, 2004 - JMD

GrIm II was been decommised April 21, 2005.

GrIm II will NO longer available for use.

Contents

Basic information to know...

Offsets

A GRIM Spectroscopy Primer

GRIM II Spectroscopy - Alan Watson

Other Information

Reference

Basic information to know...

IMPORTANT!!! ALWAYS check your incoming GRIM data for missing quads. Inform the observing specialist immediately if you notice any quads missing.

You should FTP your science images off from APO computers within 7 days after they are taken, otherwise they will be deleted. We DO NOT back up data locally here.

Offsets

Offset Directions for GrIm II as Viewed Using IRAF
INTERFACE: GrIm II @ f/5

           (TCC)                     (MC)                  (REMARK)   

           (TCC)                     (MC)                  (REMARK)   

Chip and Optical Characteristics

A GRIM Spectroscopy Primer

This page is intended to give the reader who is unfamiliar with the spectroscopy mode of GRIM enough basic information to be able to effectively plan observations, somewhere between a FAQ and the actual User Manual. Basic information about infrared spectroscopy is also provided for those users who are used to optical spectroscopy but may not have prior experience with spectroscopy in the near-IR regime.

Basics

A caveat about using GRIM for near-IR spectroscopy should be stated up front: the instrument was not designed to be a workhorse IR spectrometer. It was designed principally as an imager with spectroscopy as an interesting addition, albeit something of an afterthought.

The spectroscopic mode of GRIM uses a grating prism (grism) to preserve the in-line optical path from the entrance window to the detector. A slit is placed in the optical path near the grism; otherwise, slitless spectroscopy can be done in the "objective prism" mode. There are two significant consequences of using a grism rather than a more conventional grating. First, the resulting dispersion is not linear, since the dispersive effects of a prism and a grating are superimposed. Second, multiple orders are imaged simultaneously, leading to the need for a filter to be used in sequence with the grism and slit as an order-sorter. The following table gives lower and upper limits on the spectral window in spectroscopic mode for different f/ratio and filter combinations:

Note: All wavelengths are in microns. Two orders are present in J-filtered spectra.

Unlike DIS, the setup in GRIM for spectroscopy does not include a mirrored slit and slit-viewing camera; users familiar with DIS spectroscopy will find GRIM spectroscopy unfamiliar. A "View Slit" mode is available in the drop-down menu under the "Config" button in the GRIM control panel in Remark. This mode leaves the slit in place but removes the grism from the light path such that the undispersed beam from the slit is imaged onto the detector. To place an object on the slit, first take an image of the field in imaging mode, and compare this with an image in the "View Slit" mode (Note: You need only take one "View Slit" image on a given night as the slit positioning is highly repeatable.) Using the center of the slit determined by, for example, fitting a Gaussian profile, one can calculate the required offset between the slew position of an object and the position on the chip which places the object on the slit.

The slit is not aligned perfectly parallel to either the rows or the columns; the figure below shows the offset in f/5 mode:

Keep this in mind if you chose to dither the position of your object along the slit in order to make a master sky frame for calibration purposes. The derotation angle decreases quickly with f/ratio until at f/20, the slit is very nearly parallel to the CCD rows, so at higher resolutions this problem is less important. Another approach is to set a rotation of the instrument to compensate for the slit derotation, which then puts the slit along E-W. In the case of the figure, the derotation between the slit and the rows of the detector is approximately 1.4 degrees. Slewing to your field via Remark with a 0 degree object rotation places NSEW along the rows and columns with north up and east left; setting an object rotation of +1.4 degrees then makes the slit parallel to E-W.

As with GRIM imaging, three optical setups are available (f/5, f/10 and f/20). Each gives a different spectral resolution and effective slit length and width on the sky:

By f/20, the slit width on the sky is only 0.3 arcsecond, which is well below the typical site seeing in the near-IR (about 0.8 arcsecond) and even below the best seeing we ever achieve (about 0.45 arcsecond). Coupled with the lower throughput at f/20 limits the choice of targets to only the brightest. There are also corresponding problems with getting wavelength comparison spectra at f/20 due to throughput that should be considered when planning observations. Weigh these calibration issues against the higher spectral resolution.

In planning spectroscopic observations with GRIM, one should first begin by determining the spectral region(s) of interest. Next, a spectral resolution should be selected from among the f/ratios in the table above; this will be, of course, driven by science demands. Using this combination of spectral window plus spectral resolution, one can derive the required f/ratio and filter from the first table, above.

Here are some notes on GRIM spectroscopy from the instrument's early days. Most of the information is still relevant to the current configuration of GRIM.

Running GRIM In Spectroscopic Mode

Spectroscopy is a "mode" of GRIM much like imaging. By moving from one mode to another, you're changing the physical setup within the instrument. A grism/slit combination is mounted in the filter wheels allowing the two to be placed in the beam independently. This serves as a proxy slit viewing mode of sorts; by placing the slit in the beam without the grism, the projected position of the slit on the chip can be determined.

Placing your object(s) on the slit

Taking spectra

Wavecals can be obtained from the overhead HeNeAr lamps on the telescope truss, controlled with the xlamps application on tycho. As the f/ratio increases, the throughput is such that the exposure times for lamps lengthen considerably; by f/20, it is impractical to take Ar lamp spectra with the instrument mounted on the telescope. We find a much better arrangement of placing a portable lamp box with an Ar tube near the entrance window of GRIM itself. If you wish to take wavecals at high f/ratio, consult with your Observing Specialist to make arrangements.

Dithering objects along the slit

Proper sky subtraction can be done easily without explicit sky pointings for a given object by taking spectra at several positions along the slit. The analogy here is observing in imaging mode with GRIM by using one of the so-called "dither" scripts that move objects around the GRIM frame to simultaneously record both object and sky information. There are no pre-built dither scripts for dithering objects along the GRIM slit in spectroscopic mode, but such observations could easily be scripted. With a sufficient number of pointings along the slit and enough of an offset between pointings, all object spectra for a given filter and exposure time can be median-combined (with a high/low sigma pixel rejection algorithm) to result in an average sky frame in spectral space. Simply subtracting this resulting sky frame off of the appropriate object spectra takes care of all your calibrations at once: bias, dark current, and flat fielding. Alternately, one can obtain explicit calibration frames and apply them to all the raw data before making the median sky image, arriving at the same result. Note, however, that due to software limitations, it's not possible to take true bias frames with GRIM, given that the shortest permissible exposure time is 1.2 s.

Dithering object positions along the slit is complicated slightly at the lower f/ratios by the fact that the slit is not parallel to the rows of the chip. Therefore, in instrument coordinates, a combination of both x and y motion is required to move from one location to another along the slit. (A plot of the GRIM slit center across the chip can be found here.) However, as mentioned previously, by performing a small rotation one can align the slit with E-W on the sky and then do offsets in object coordinates to simplify the dithering process to one dimension. Recent measurements of the slit position separated by several months show that the positioning of the slit relative to the chip is highly repeatable, so again there is no need to take repeated "View Slit" images throughout the night to confirm slit position.

Wavelength Calibrations

Wavelength calibrations can be obtained in different ways. Argon lamp spectra can be taken off the mirror covers as with DIS; labeled plots taken with GRIM are available here. Alternately, night sky (OH 'airglow') lines can be measured in sky exposures to provide a wavelength reference. A spectral atlas of OH lines in the ~1 - 2.25 micron region is available in Rousselot et al. (2000). Another resource for both arc lamp as well as night-sky spectra in the near-IR is available at the Joint Astronomy Centre site. For on-site observers, we have this atlas and some additional print resources available in the 3.5m control room for on-site use or photocopying.

A set of line plots of argon lamp spectra taken with various modes of GRIM is available; the modes are JHKK'K_s at f/5, f/10 and f/20. 

Data Reduction

The resulting images can be reduced as normal spectroscopic data. Be sure to set the FITS card "DISPAXIS" equal to 2, since the dispersion is parallel to the columns of the detector.

GRIM II Spectroscopy

From: Alan Watson

Submitted: Tue, 24 Oct 95 17:43:25 -0600

On 19/20 October 1995 we used GRIM II to attempt spectroscopy of the
2.3 micron CO absorption band in stellar clusters. We used the f/10
optics and slit. On the whole, things worked well, although there are
some peculiarities to be overcome. Here are some comments that may
help other observers.

Alan Watson & Jon Holtzman

Throughput

We obtained a peak signal of 500 DN/s/pixel (28 DN/s/A) and a total
signal of 2500 DN/s/pixel (140 DN/s/A) from a K = 6.5 star under
conditions of clear skies and 1.2ish arcsec seeing.

Columns 128 and 256

Columns 128 and 256 seem to be offset down by one row.

Read Noise

Our typical backgrounds in 60s were about 100 DN (about 500 e), and
so for faint objects our noise is utterly dominated by the read
noise of about 110 e. We can think of three ways to improve this
situation: integrate longer; reduce the read noise; or implement
multiple reads. However, since we would have to integrate for 1500s
for the background noise to equal the read noise, reducing the
effective read noise seems very desirable. Implementing a quadruple
read scheme or halving the read noise, neither of which are at all
unreasonable goals, would increase the efficiency of spectroscopy by
a factor of four.

Bias Fluctuations

In our object-sky subtractions we saw banding parallel to the rows
in almost every exposure. The pattern of the banding was similar in
each quadrant, suggesting fluctuations in the bias. About 20% of
our exposures had banding with a peak-to-peak magnitude of about 100
DN in the low rows of each quadrant. In the remainder, the banding
had a peak-to-peak magnitude of 15-30 DN and more variable
structure. Since our primary targets (K about 12.5) had only about
100 DN peak signal in 60s, this banding was a very serious concern.

We were able to significantly reduce the level of the banding by
averaging portions of rows well away from the spectrum to determine
a bias level for each row. Since the spectral dispersion is not
perfectly parallel to the columns of the detector, this will only
work well if the residuals from sky lines in object-sky subtractions
are small. For stellar objects, a background aperture close to the
object aperture may work well.

Do people find this banding a problem in low background (i.e.,
narrow band) imaging?

Flats

The quartz lamps were too dim for flats. We used the incandescent
lights which gave a few thousand DN in 10s.

Wavelength Calibration

Wavelength calibration of CO band spectroscopy is difficult because
of the paucity of emission lines in the 2.3 micron region in each of
the three standard sources of emission lines: planetary nebulae, HII
regions, and the night sky.

We attempted to obtain an Ar spectrum using the conventional set up:
lamps shining onto the enclosure from behind the secondary. We
detected four lines in a 300s lamps on/off pair, with peaks of about
100 DN in the brightest two. At the suggestion of Dan Long, we
obtained much better spectra by removing the instrument from the
telescope and placing a lamp on a step ladder directly in front of
the dewar window; we obtained good signal on about a dozen lines
spread across the K window in exposures shorter than 1 second. In
retrospect, we think it might be possible to do this without
removing the instrument from the telescope by pointing the telescope
close to the horizon and placing the lamp between the instrument and
the tertiary.

Bruce and Karen are investigating Xe and Kr lamps, as these may turn
out to have brighter lines and be suitable for use with the
conventional set up.

We can supply line lists for OH, Ar, Xe, and Kr.

Other Information

GRIM II, the ARC near-infrared camera, combines broadband and narrowband imaging and low resolution slit spectroscopic capabilities into a single instrument.

• Users Manual (pdf): This manual is the most comprehensive guide to observing with Grim II.
• How to Use the Dither Script
• An Important Message About GRIM2 Images in FITS and IRAF Formats.
• Bad Pixel Mask
• Spectrophotometric standards for use with GRIM
• Grim ICC commands

Get a PostScript User's Manual here

Some documentation on the dither script here

Imaging

The image header variables FILTER1, FILTER2, LENS, GRISM, SLIT give the current status of GRIM II's mechanical configuration. The Numbers that follow are the position the filter/lens/grism/slit wheel is placed in. Below is a key:

. Lens F/5 -- 1 LENS F/10 -- 3 LENS F/20 -- 5 LENS. Grism GRISM_OUT -- 2 GRISM GRISM_IN -- 3 GRISM ND_3 -- 5 GRISM ND_13 -- 6 GRISM ND_25 -- 7 GRISM Slit NO_SLIT -- 7 SLIT 240_MICRON -- 1 SLIT 120_MICRON -- 2 SLIT 60_MICRON_LONG -- 3 SLIT 60_MICRON_MID -- 4 SLIT 60_MICRON_SHORT -- 5 SLIT

Filters (OPEN1) -- 13 FILTER1 (OPEN2) -- 13 FILTER2 J_BAND -- 1 FILTER1 (OPEN2) H_BAND -- 2 FILTER1 (OPEN2) K_BAND -- 3 FILTER1 (OPEN2) K_PRIME -- 4 FILTER1 (OPEN2) K_SHORT -- 5 FILTER1 (OPEN2) K_CONT -- 6 FILTER1 (OPEN2) K_DARK -- 7 FILTER1 (OPEN2) 1.580 -- 8 FILTER1 (OPEN2) 1.700 -- 9 FILTER1 (OPEN2) 1.083 -- 1 FILTER2 (OPEN1) 1.094 -- 2 FILTER2 (OPEN1) 1.237 -- 3 FILTER2 (OPEN1) 1.282 -- 4 FILTER2 (OPEN1) 1.644 -- 5 FILTER2 (OPEN1) 1.99 -- 6 FILTER2 (OPEN1) 2.122 -- 7 FILTER2 (OPEN1) 2.166 -- 8 FILTER2 (OPEN1) 2.22 -- 9 FILTER2 (OPEN1) 2.248 -- 10 FILTER2 (OPEN1) 2.295 -- 11 FILTER2 (OPEN1) 2.36 -- 12 FILTER2 (OPEN1)

---

NAME CENTER(µm) FWHM(µm)
-------------------------------------
J (1.25) 0.30
H (1.65) 0.30
K (2.20) 0.40
Steam (1.99) 1%
H2 =1->0 S(1) (2.122) 1%
Br (2.166) 1%
CO Continuum (2.22) 4%
CO Band (2.36) 4%
He I 1.0829 0.0136
Pa Gamma 1.0940 0.0104
O II 1.236 0.0105
Pa Beta 1.2823 0.0146
Fe II 1.6471 0.0176
H2 =2->1 S(1) 2.2485 0.0239
CO2->0 Bandhead 2.2973 0.0274
Mauna Kea K' 2.1235 0.3370
Short K 2.155 0.33
Continuum K 2.2597 0.0531
K dark (2.27-2.43)
Narrow Cont. (1.580) 0.010
Methane (1.700) 0.050
You can download a single Postscript file of ALL of these plots here

Spectroscopy Details - The very comprehensive documentation from Univ. of Chicago

GRIM II, the ARC near-infrared camera, combines broadband and narrowband imaging and low resolution slit spectroscopic capabilities into a single instrument.

A GRIM Spectroscopy Primer
• Grim Command Line keyword manual

Detector Characteristics

Grim II's HgCdTe detector array is sensitive to wavelengths of 1 to 2.5 µm. The sensor is a 256 x 256 detector NICMOS 3 focal plane array made by the Rockwell International Science Center (RISC). The characteristics of the current detector array are summarized on the GRIM II Detector Characteristics page and on the APO Detector Characteristics page. Note: The GRIM II detector reaches soft saturation (non-linearity) at 28,000 counts.

Gain

submitted by K. Gloria - results are nominal

I used the bad weather we had in December, 1994 to measure the gain of the GRIM2 detector. To do this I took pairs (A, B) of flat fields in f/5 mode, through the J filter, with a constant source of illumination (in this case a quartz-halogen lamp). I did this for a wide range of integration times. After bias and dark subtracting the images, I utilized Poissonian statistics to determine the gain of the detector by plotting the variance of ((A - B)/sqrt 2) vs. ((A + B)/2). The gain = 1/slope of this graph. For the linear regime of the detector, I obtained a value of gain = 4.56 e-/ADU.

gain plot

Imaging

GRIM II provides three imaging scales, allowing measurements which begin to approach the telescope's diffraction limit at 2.2 µm. GRIM II's optics were designed to be fed by the APO 3.5-m (f/10) telescope. GRIM II's f/5 scale allows wide field measurements, with a field size near 1.5 arcminutes on a side. The imaging scales are listed on the APO Detector Characteristics page.

Filters

GRIM II has two filter wheels, which together can hold a maximum of 24 filters. The current filter set provides for basic broadband and narrowband imaging. The filters are listed on the APO GRIM II filters page. Transmission curves are available on University of Chicago's GRIM II filters (not maintained by APO) page.

The image header variables FILTER1, FILTER2, LENS, GRISM, SLIT give the current status of GRIM II's mechanical configuration. The Numbers that follow are the position the filter/lens/grism/slit wheel is placed in. Here is a key;

• Lens
• • F/5 -- 1 LENS
• • F/10 -- 3 LENS
• • F/20 -- 5 LENS

• GRISM_OUT -- 2 GRISM
• GRISM_IN -- 3 GRISM
• ND_3 -- 5 GRISM
• ND_13 -- 6 GRISM
• ND_25 -- 7 GRISM

• NO_SLIT -- 7 SLIT
• 240_MICRON -- 1 SLIT
• 120_MICRON -- 2 SLIT
• 60_MICRON_LONG -- 3 SLIT
• 60_MICRON_MID -- 4 SLIT
• 60_MICRON_SHORT -- 5 SLIT

• (OPEN1) -- 13 FILTER1
• (OPEN2) -- 13 FILTER2
• J_BAND -- 1 FILTER1 (OPEN2)
• H_BAND -- 2 FILTER1 (OPEN2)
• K_BAND -- 3 FILTER1 (OPEN2)
• K_PRIME -- 4 FILTER1 (OPEN2)
• K_SHORT -- 5 FILTER1 (OPEN2)
• K_CONT -- 6 FILTER1 (OPEN2)
• K_DARK -- 7 FILTER1 (OPEN2)
• 1.580 -- 8 FILTER1 (OPEN2)
• 1.700 -- 9 FILTER1 (OPEN2)
• 1.083 -- 1 FILTER2 (OPEN1)
• 1.094 -- 2 FILTER2 (OPEN1)
• 1.237 -- 3 FILTER2 (OPEN1)
• 1.282 -- 4 FILTER2 (OPEN1)
• 1.644 -- 5 FILTER2 (OPEN1)
• 1.99 -- 6 FILTER2 (OPEN1)
• 2.122 -- 7 FILTER2 (OPEN1)
• 2.166 -- 8 FILTER2 (OPEN1)
• 2.22 -- 9 FILTER2 (OPEN1)
• 2.248 -- 10 FILTER2 (OPEN1)
• 2.295 -- 11 FILTER2 (OPEN1)
• 2.36 -- 12 FILTER2 (OPEN1)

Spectroscopy

Spectroscopy can be done with or without a cold slit. The cold slit wheel has positions for as many as six slits. Table 2 shows the range of spectral resolution with the currently available slits. Additionally, a 20 µm pinhole is available for diagnostics.

Labeled Argon Lamp Plots for wavelength-calibrating spectra taken with GRIM

GRIM II Spectral Wavelength Coverage

===============================================================================
		J Band(Order 6)	J Band(Order 5)	H Band(Order 4)	K Band(Order 3)	
Scale and Slit	(low)	(high)	(low)	(high)	(low)	(high)	(low)	(high)
_______________________________________________________________________________
f/5		0.844	1.301	1.013	1.561	1.266	1.951	1.688	2.602	
f/10		0.958	1.187	1.150	1.424	1.437	1.780	1.916	2.373	
f/20 Short	0.970	1.082	1.163	1.298	1.454	1.622	1.939	2.163	
f/20 Mid	1.015	1.127	1.217	1.352	1.522	1.690	2.029	2.253	
f/20 Long	1.068	1.180	1.282	1.415	1.602	1.769	2.136	2.359	
===============================================================================
Note: There is order overlap in the J band.                                    

Slits & Resolution

The dispersion direction is along the columns of the detector. In f/5 mode, wavelength increases with decreasing row number on the image. In f/10 and f/20 modes, wavelength decreases with decreasing row number.

Additional Information

University of Chicago's GRIM II page - newly revised and expanded (not maintained by APO)

Grim Command Line Keyword Manual (Craig has these on a separate web page.  Put link here and delete this!)

Last updated 13 August 2003 by JCB

GRIM can be commanded directly via keywords issued either in the MC or directly to the instrument control computer (ICC). Addressing the instrument directly allows for scripting of observations outside of Remark. This document summarizes both types of GRIM keywords and provides usage examples.

Also see the GRIM configuration and keyword file (FIND THIS TXT FILE!!!)

The GRIm ICC commandsThis is a reverse-engineered command set for the GRIm ICC from the GRIm Postscript manual, the main APO GRIm page, and what one sees from Remark commands are the sources. I include example return keys seen from one unrepresentative command attempt.

auto

Description:

Usage: auto: x y (x and y Boolean TRUE=1 FALSE=0)

Example keywords:

iccversion

Description:

Usage: iccversion:

Example keywords: GRIMTXT="2.52 12/1/2000"

init

Description:

Usage: init:

Example keywords: [nothing]

integrate

Description: Integrate for n milliseconds. The integrate: argument includes the time for the first reset and read, plus some unknown overhead. This all takes 1.21s, and requesting an integration of less than 121ms will yield increasingly bizarre images.

Usage: integrate: n

Example keywords: GRIMTXT="chip has been read"; OPENTIME=0.909000; STARTTIME=06:31:36; STARTDATE=07/14/2003; STOPTIME=06:31:37; BZERO=22768.0; BSCALE=1.0; filter1=1; filter2=13; lens=1; grism=2; slit=7; grimmode=0; grimscale=1; grimfilter=1

motorversion

Description:

Usage: motorversion:

Example keywords: GRIMTXT="38.05/23/96"

move

Description: Move the motors. There are actually more than three motors, but all but the half-wave plate state can be described with three arguments. In particular, there are two filter wheels, and a slit wheel whose position is determined by the scale argument..

Usage: move: mode scale filter (mode, scale and filter parameters from the lists below)

Example: move 0 5

mode parameters:

0 - Image
1 - Spectral (grism with slit)
2 - View slit (image with slit)
3 - Object prism (grism without slit)
4 - Image ND3%
5 - Image ND13%
6 - Image ND25%
7 - Polarimetry

scale (or camera) parameters

1 - f/5
3 - f/10
5 - f/20
13 - f/20 short
21 - f/20 long filter

filter parameters

0 - Dark blank-off
1 - J [filter1=1, filter2=13]
2 - H [filter1=2, filter2=13]
3 - K [filter1=3, filter2=13]
4 - K'
5 - K short
6 - K continuum
7 - K dark
8 - 1.580 BP 0.010
9 - 1.700 BP 0.050
13 - Open
15 - 1.083um
16 - 1.094um
17 - 1.237um
18 - 1.282um
19 - 1.644um
20 - 1.99um
21 - 2.122um
22 - 2.166um
23 - 2.22um
24 - 2.248um
25 - 2.295um
26 - 2.36um

Example keywords:
filter1=0 filter2=13 lens=0 grism=2 slit=7 grimmode=0 grimscale=0 grimfilter=0

move hwp: p Is this really two words, or movehwp:? -- CPL

Example keywords:
Not with this version of the GRIM ICC. movedark

Usage: movedark:Configures the instrument to take dark frames. Use any move command to take other types of image.
Example keywords:
filter1=0 filter2=0 lens=5 grism=0 slit=0 grimmode=-1 grimscale=5 grimfilter=0 pingUsage: ping:Example keywords:
GRIMTXT="good ping" statusUsage: status:The grimmode, grimscale, and grimfilter keys correspond to the respective move: command arguments. The other motor commands describe the state of the actual motors. grimmode - ....

Usage: grimmode:

Same as the move: command's mode argument.
But can be -1 when grimdark: selected.

grimscale - ....

Usage: grimscale:

Same as the move: command's scale argument and the lens keyword.

grimfilter - ....

Same as the move: command's filter argument.

lens - the image scale, or camera, or lens.

1 - F/5
3 - F/10
5 - F/20

grism - ....

2 - GRISM_OUT
3 - GRISM_IN
5 - ND_3
6 - ND_13
7 - ND_25

slit - The "right" slit is selected, based on the move command's scale argument.

1 - 240_MICRON (f/5)
2 - 120_MICRON (f/10)
3 - 60_MICRON_LONG (f/20 long)
4 - 60_MICRON_MID (f/20)
5 - 60_MICRON_SHORT (f/20 short)
7 - NO_SLIT

filter1

Usage: filter1:

Position of the FILTER1 motor.

filter2

Usage: filter2:

Position of the FILTER2 motor.

Example keywords:
CAMERA="idle" BZERO=22768.0 BSCALE=1.0 INTMODE="idle" INTSTATUS="idle" filter1=2 filter2=13 lens=3 grism=2 slit=7 grimmode=0 grimscale=3 grimfilter=2

temperatures

Usage: temperatures:

The instrument has a number of sensors, but APO only knows to hope for those listed to the left of the No Connection sensors to go from outside the instrument in. The sensors fairly regularily read 383.08 across the board, and characters in the string are often dropped when the instrument is under load.
Example keywords:
gtemp="276.60 103.24 099.28 093.12 089.60 084.32 075.52 076.40 N/C N/C N/C N/C 383.08 304.76 081.68 282.76 "

time

Usage: time:

Returns the OPENTIME value described in the original GRIm manual.
Example keywords:
TIME=98909

 GRIM MC Commands

grim

Usage: grim string

Send an arbitrary command to the grim

Most grim commands have colons, as in grimstatus = grim status:

grimabort

Usage: grimabort

?Send abort: to the grim

?Grim will finish the current exposure but cut short the integration time

grimdark

?Usage: grimdark

?Take a single dark frame

grimping

Usage: grimping

?See if the grim icc is talking to its electronics

?Returns after 8 seconds if it's not; otherwise returns immediately

grimstatus

Usage: grimstatus

?See if the grim icc is talking to it's other electronics

?Show status of grim filter,focus, grism, etc

grimiccversion

?Usage: grimiccversion

?Echo version of current GRIM control software to the screen

grimmotorversion

?Usage: grimmotorversion

?Echo version of current GRIM motors to the screen

grimtime

?Usage: grimtime

?how much time exposed

grimtemperatures

?Usage: grimtemperatures, grimtemp

?Echo temperatures of various internal GRIM components to the screen

?

griminit

?Usage: griminit

?Re-initialize GRIM

grimauto

?Usage: grimauto x y

?should the grim readout every time x=1

?should the grim transfer the image to the hub y=1

grimmove

?Usage: grimmove x y z

?Send the motors to new positions x, y, z

grimcall

 

?Usage: grimcall

?

?Make the grim mac call for help in an unnatural voice

move hwp: p