SOAR AEON Features and News

What configurations are offered in AEON-mode at SOAR?

As of 2023A AEON at SOAR offers spectroscopy from the UV out to 2.4 um, and imaging at visible wavelengths. Optical spectroscopy is done with the Goodman High Throughput Spectrograph (GHTS), at various spectral resolutions.  Near-IR spectra are obtained with the Triple Spec 4.1 (TSpec) spectrograph at a fixed resolution R~3500.

Standard Features for Goodman in AEON mode

• Spectroscopy: We always have the 400 line grating available.
  • The 400M1 (300-705nm) and 400M2 (with GG455 filter, 500-905nm) configurations are available with the RED camera. Only the 400M1 is used with the BLUE camera. These setups use the 1" wide long slit and 2x2 binning. 
  • Other configurations have/are been used in AEON mode are therefore also available if requested:
    • 400M1 and 400M2 with 1.5" wide slit, 2x2 binning
    • 600 line grating in  600MID (with GG395 filter, 435-702nm) and 600RED (with GG-495 filter, 630-893nm) setups, 1" longslit, 2x2 binning.
    • 600 line grating (blue optimized) in the 600UV setup (3010-5690A), with 1" and 1.5" slits, 2x2 binning
    • 930 line grating in 930M2 setup, 0.45" wide longslit and 1x2 binning
    • 930M2 with 1" longslit and 2x2 binning.
    • 2100 grating centered at 3900A with 0.45" slit and 1x2 binning (3585-4215A, R~11900)
    • 2100 grating centered at 5000A with 1" slit and 1x2 binning (4685-5315A, R~5950)
    • 2100 grating centered at 6508A, with 0.45 arcsec slit and 1x2 binning (6130-6710A, R~11900)
    • The GHTS can be configured with other gratings and long slits, contact us if you have different requirements (see below).

• Imaging: we normally use the Sloan SDSS-g,r,i,z with the RED camera, and the SDSS-g,r,i and a wide VR with the BLUE camera. Other filters are available upon request. See the filter page.

Bottom line is: if you think your science case will benefit from the AEON-mode queue at SOAR but requires a different Goodman configuration than those listed here, contact us (cesar.briceno at noirlab.edu) to discuss if we can add it to the existing set of AEON-mode configurations.

• Atmospheric Dispersion Corrector (ADC) always IN, which means users can request any position angle (PA) they need. If this option is not selected in the Las Cumbres Observation portal, the system will default to a PA=0 deg.
• Guide Star and on-slit target acquisition: manual
• Daytime Calibrations: bias, and flats ran every afternoon by SOAR staff.  All daytime calibration data will be publicly available at the LCOGT Observation Portal.
• Night time Calibrations: Every night (weather permitting) we will also obtain a observation of a spectrophometric standard in each of the three spectroscopic configurations indicated above.  The spectrophotometric standard star observations, like the daytime calibrations, are also publicly available to all AEON users.
  • Users can request comparison lamps (ARC) to be taken together with their science frames. The software at the SOAR end will select the appropriate lamp (HgArNe or CuHeAr) and exposure time. All setups use the brighter HgArNe lamp, except for blue and UV setups with the higher resolution gratings (930 lines/mm and higher), which use the CuHeAr lamp. ARCs can be requested before or/and after the science frame. Users can also request a quartz lamp-flat together with their science frames; again, users need only set the number of frames in their observation request, as the correct expsure time is set by the software at the SOAR end. However, we find dome flats work well for most cases.
• Standard star observation: a spectrophotometric standard star will be observed at the beginning of every scheduled AEON night, in all spectroscopic setups, together with the corresponding arc lamp spectra. These data will be publicly available to all users, as part of the calibration data. The standard star observation will take place during twilight at the beginning of the night, or whenever the telescope can start observing, if weather conditions did not allow opening at sunset.  Any other standard observations, like radial velocity standards, should be requested together with the science targets, in a single observation block to ensure they are observed right before or after the science target.
• OVERHEADS. Because the AEON queue is created dynamically by an unsupervised software, every AEON Observation Request is initially set up with specific overheads. The scheduler starts out with the following overheads:
  • 180s front padding for each observation. This is meant to take into account the slew to the new target (allows for telescope slew, Nasmyth rotator move, and dome reaching its appropriate position).
  • 30s for Goodman configuration changes. Examples: changing from one spectroscopic setup to another, changing from spectroscopic to imaging mode, changing from ARC to science target or viceversa.
  • 10s fixed overhead for readout
  • 5s fixed overhead per exposure.
  • Spectroscopy: 900s for target acquisition (includes guide star acquisition).
  • Imaging: 30s overhead for guide star acquisition.
  • ARCs: a comparison spectrum with the HgArNe lamp and the low resolution gratings (400 and 600 line/mm) takes ~1min. This includes the 30s indicated above for configuration change, a 10s warmup time for the lamp, the exposure time and readout time. Higher resolution gratings at blue wavelengths, like the 930M2 mode, require the CuHeAr lamp, which takes ~3min.  Users need only specify what ARC spectrum they need when setting up an Observation Request at the Las Cumbres Observation Portal; the appropriate exposure times are set automatically by the control software at SOAR.
  • Telluric standards: on average, a Telluric star observation will take ~6min, which is added to your TSPec observation.

Standard Features for TripleSpec in AEON mode

• Default Instrument Position Angle = 90 deg.
• Fixed configuration: TripleSPec4.1 features a fixed slit  1.1-arcsec wide by 28-arcsec long. Spectra cover a simultaneous wavelength range of 0.95 to 2.47 microns, at a spectral resolution R~3500.
• Daytime Calibrations: flats (amps ON and lamps OFF), and ARCs, ran every afternoon by SOAR staff.  All daytime calibration data will be publicly available at the LCOGT Observation Portal.
• Guide Star and on-slit target acquisition: manual
• Fixed dither pattern ABBA for al targets (both science and telluric standards) with 12.7 arcsec separation between A and B positions.
• Night time calibrations: there are only two night time calibrations applicable to TSPec, ARCs and Telluric Standard observations. CuHeAr comparison lamps are taken during the afternoon calibrations.  Though you can specify an ARC before or after your target, this is not usual practice with TSPec, since the spectrograph is quite stable, and ARCs taken in the afternoon suffice for almost all requirements. Allowance for small wavelength shifts, using the telluric, is incorporated into the TSPec pipeline. A Telluric standard observation will be automatically added immediately after all TSPec science targets; the observation is automatically set by our software at SOAR so that the difference in airmass between the science target and the telluric is < 0.1.
• OVERHEADS. Because the AEON queue is created dynamically by an unsupervised software, every AEON Observation Request is initially set up with specific overheads. The scheduler starts out with the following overheads:
  • 180s front padding for each observation. This is meant to take into account the slew to the new target (allows for telescope slew, Nasmyth rotator move, and dome reaching its appropriate position).
  • 900s for target acquisition (includes guide star acquisition).
  • ARCs: As said above, ARCs are not usually done at night time with TSPec, but if you insist in obtaining an ARC, it will add about 65s to your observation duration.
  • Telluric standards: on average, a Telluric star observation will take ~6min, which is added to your TSPec observation.

Note that when the observation is executed, the control software at SOAR sends real-time updates of the status of each part of the observation process (e.g., actual start and end of target acquisition). This means that the actual overheads are adjusted in real time. For example, for most targets the acquisition time is less than the estimated 20min. At the end of the observation the actual elapsed time is used at Las Cumbres to 1) update the schedule and 2) compute the actual time to be charged to the program. The scheduler updates roughly every minute. This means that the content of the queue may, and on most nights does change during the night, depending on how smoothly the observations progress.  For proposing for AEON on SOAR, users should use the full overheads as described above.

If for some reason the observation takes longer to get started, there is an allowance of a few minutes before it is aborted. Such occasions are rare.

2023B Semester

AEON scheduled on 44 nights (37 nights with the Goodman RED camera and 7 nights with the Goodman BLUE camera - see the 2023B calendar), for 15 regular programs and 10 Target of Opportunity (ToO) programs, totaling 440h: 19 programs with Goodman, and 6 programs with TSPec.  Following the requirements of the various Goodman programs, this semester we offer the following configurations with the Goodman instrument:

- BLUE camera configurations:
Spectroscopic:

- 400M1 with 1 arcsec slit and 2x2 binning. Coverage: 3000-7050A; 3-pixel resolution=~13A

- 600UV with 1 arcsec slit and 2x2 binning. Coverage: 3010-5690A: 3-pixel resolution=~7A

- 600UV with 1.5 arcsec slit and 2x2 binning. Coverage: 3010-5690A: 3-pixel resolution=~7A

- 2100@3900A, with 0.45 arcsec slit. Coverage: 3585-4215A, 3-pixelresolution=~0.9A

Imaging: SDSS-g, r, i, CO+ filter  all in 2x2 binning

- RED camera configurations:
Spectroscopic:

- 400M1 with 1 arcsec slit and 2x2 binning. Coverage. 3000-7050A; 3-pixel resolution=~13A

- 400M2+GG455 filter, with 1 arcsec slit and 2x2 binning. Coverage: 5000-9050A; 3-pixel resolution=~13A

- 2100@5000A, with 1 arcsec slit. Coverage: 4685-5315A, 3-pixelresolution=~0.9A

Imaging: SDSS-g, r, i, z,  all in 2x2 binning

2023A Semester

AEON scheduled on 36 nights (26 nights with the Goodman RED camera and 10 nights with the Goodman BLUE camera - see the 2023A calendar), for 14 programs totaling 360h: 10 programs with Goodman, and 4 programs with TSPec.  Following the requirements of the various Goodman programs, this semester we only offer only the 400 line/mm grating in spectroscopic mode in Goodman. Imaging with Goodman will use the SDSS-g,r,i,z filters when the RED cammera is installed, and the SDSS-g,r,i and the wide VR filter, on nights using the Goodman BLUE camera.

2022B Semester

NEW: TSpec 4.1 near-IR spectrograph available in AEON Mode.

AEON scheduled on 41 nights, for 16 programs totaling 374h: 13 programs with Goodman, and 3 programs with TSPec.

With both Goodman spectrograph/imager instrument and TSpec 4.1 near-IR spectrograph, users can now obtain spectroscopy of their targets spanning the entire optical wavelength range, from the atmospheric cutoff, and going out to the near-IR, to 2.2 microns (K-band).  Observations with TSpec in 2022B will be limited to a simple ABBA dither pattern; the separation between the A and the B position is 12.7 arcsec. The overhead for changing from Goodman to TSpec and viceversa is 2 min.

A simple Exposure Time Calculator can be found in the TSPec page.

TSpec4.1 is the same instrument formerly known as ARCOIRIS, previously installed at the f/8 focus of the 4m Blanco telescope at CTIO. Users should note that because at SOAR TSPec  is fed by reflection off a dichroic, which also transmits light to the guider, the response cuts off below 1.0 microns. The nominal point of 50% reflectivity of the dichroic is around 0.95 microns. A comparison between the response on Blanco and SOAR can be found at this page.

2022A Semester

A total of 24 nights (240h) for 12 programs have been scheduled in AEON-queue mode at SOAR for 2022A.

Both Goodman BLUE and RED cameras are available.  Since demand is highest for the RED camera, most nights (18 out of the 24) are allocated with this detector. However, users should note that the RED camera is comparable in sensitivity to the BLUE down to around 4000A. More details about the advantages and caveats for each detector are described in the Goodman Instrument Characteristics page.

NEW: Programs can request targets for either camera, and will also be able to request observations in either spectroscopic or imaging mode. Las Cumbres Observatory will simply keep the accounting of used hours against the total time allocated to each program, regardless of which camera has been used, or which mode.

Because selecting one or the other detector is a daytime task, users are limited to using the camera scheduled for that particular night. However, imaging and spectroscopy capabilities are always available with both cameras; for example, an user can submit a request for images AND spectra of the same object, of course, only with the configurations supported by AEON. See below for the configurations supported this semester.

Detector noise characteristics for AEON data:
All AEON data are collected using a single fixed readout mode: 344ATTN3 for the RED camera, which corresponds to a readout noise= 3.9 e-,  and gain=1.5 e-/ADU, and 200ATTN0 for the BLUE camera, which corresponds to a readout noise=4.7e-,  and gain=1.4 e-/ADU (see the Goodman Cheat Sheet). The readout, region of interest and binning are set automatically for each mode and are not user-selectable, therefore users will not see these as options in the Las Cumbres Observation Portal. Users only have the option to request the appropriate mode (e.g., 400M1 if requesting a spectroscopic observation, or the filter if it is an imaging observation).