SOAR AEON Features and News

Standard Features for Goodman

  • 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
  • Calibrations: BIAS, FLATS; scripted, ran every afternoon by SOAR staff.  Every night (weather permitting) we will also obtain a observation of a spectrophometric standard in each of the three spectroscopic configurations indicated above. All calibration data will be publicly available at the LCOGT Observation Portal. 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. An ARC frame takes ~1min for a HgArNe lamp, and ~3min for the CuHeAr lamp (including overheads for moving the comparison mirror in/out, turning the lamps on/off, allowing 10s for lamp warm up, and 8.5s for readout). 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 configuration changes. Examples: changing from spectrograph setup to another, changing from spectroscopic to imaging mode, changing from an ARC spectrum to a science spectrum or viceversa.
    • 10s fixed overhead for readout
    • 5s fixed overhead per exposure.
    • Spectroscopy: 1200s 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. Higher resolution gratings at blue wavelengths, like the 930M2 mode, require the CuHeAr lamp, which takes 2min.  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.

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.

2022B Semester

NEW: TSpec available in AEON Mode. For the 2022B semester we are offering the TSpec 4.1 near-IR spectrograph, in addition to the Goodman spectrograph/imager instrument in AEON mode. This is an important development, as it means that users can now request 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).  We are working on implementing TSpec such that users can request back to back Goodman optical and TSPec near-IR spectra of a particular target.  To enable this feature, users will need to make sure they include Goodman and TSPec as two configurations within the same Observation Request. Observations with TSpec in 2022B will be limited to a simple ABBA dither pattern. 

The overhead for changing from Goodman to TSpec and viceversa is 2 min.

Users should indicate the J-magnitude of their target, and total exposure time needed. A simple Exposure Time Calculator can be found in the TSPec page.

TSpec4.1 is the same instrument known as ARCOIRIS, formerly installed at the f/8 focus of the 4m Blanco telescope on CTIO. Users should note that because on SOAR TSPec  is fed by a 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).