- Post-processing data with the new EMIR H2RG detector
- EMIR upgrade with new H2RG detector
- EMIR installed (back) at Nasmyth A
- EMIR Maintenance stand-down (March-June 2023)
- EMIR CSU degradation
- EMIR FITS Update
- EMIR RAMS improvement
- EMIR Science Verification Update II
- EMIR Science Verification Update
- Happy Holidays from the EMIR team
- EMIR arrives at the GTC!!
- EMIR last steps!!!
October 2024
Subject: Post-processing data with the new EMIR H2RG detector
Despite the new EMIR H2RG detector is much more sensitive and stable than the previous one, it is not free from certain undesirable artifacts that need to be corrected in post-processing.
In this note, EMIR users can find details on how to perform the processing to enhance the EMIR H2RG data quality.
December 2023
Subject: EMIR upgrade with new H2RG detector
On sky tests with the new H2RG detector for EMIR have been completed successfully in November-December 2023, producing the new control software and the corresponding operational tools that made EMIR available for science operations again since late December 2023.
Perfomance of this new H2RG detector is notably better than the obtained with old H2 detector, making EMIR more sensitive than before. Comparison with previously observed data (see Figure below) clearly demonstrates the gain in sensitivity with the current instrument configuration.
In an operative sense, observations with the current H2RG detector produce the S/N predicted by EMIR ETC.
As a side effect to ensure this better perfomance, H2RG needs some time to signal stabilization, which implies that EMIR operation has now higher overheads than before: observing efficiency is 50% in imaging mode and 75% in spectroscopic modes.
Finally, due to problems found with one of the electronic cards, CSU fine tuning for Multi-Object Spectroscopy is still in progress, delaying the scientific operations in this mode. However, some workarounds are used in order to allow the execution of the programmed observations with EMIR MOS.
July-August 2023
Subject: EMIR installed (back) at Nasmyth A
Once completed the CSU maintenance works and after installed the new H2RG CCD detector, EMIR was mounted back again at Nasmyth A focal station on July 28th, 2023. Instrument cooldown was launched on August 4th, 2023, in order to resume the science operations when the nominal operation temperature of the instrument will be achieved.
The first on sky tests with these new components are planned for the second week of August, with the aim to complete some science observations in imaging and longslit spectroscopy modes before the end of semester 2023A.
March 2023
Subject: EMIR Maintenance stand-down (March-June 2023)
EMIR planned stand down for maintenance works was finally scheduled for March 2023. At this moment, instrument was warmed up and moved from Nasmyth A platform to conduct a series of internal procedures in order to recover the complete functionality of the instrument. These works include the replacement of CSU piezoelectric components and slit friction pads, and more impontantly, the use a of new upgraded Hawaii H2RG detector that will solve the lack of sensitivity previously noted at fainter magnitudes in EMIR.
CSU maintenance works are expected to be completed in April 2023 while the new CCD installation and their associated works will be developed during May-June 2023, with the aim of resuming the science operations with EMIR in July 2023.
June 2022
Subject: EMIR CSU degradation
EMIR CSU lifecycle is nearly ended, hence its performance is being affected in some manner. Since June 2022, slits 101 and 35 are currently working in a degraded mode: while slit 101 is permanently stucked, slit 35 needs to be configured fully closed during longslit observations (something that is taken into account during the data acquisition in order to not place the target in any of the affected positions). The impact on the scientific observations is alleviated during the data reduction, but in any case, users should be aware of this effect when inspecting the raw data files produced with EMIR from June 2022 onwards.
Next figures show examples of raw data obtained with degraded slits both in EMIR imaging and longslit spectroscopy modes, and how the data reduction process can perfectly deal with these.
Next EMIR maintenace works are planned for late 2022, when CSU piezoelectric components and slit friction pads will be replaced in order to restore the full CSU functionality.
March 2019
Subject: EMIR FITS Update
Beginning in semester 19A, from March 1 2019 onwards, the EMIR control system incorporates two changes that we hope will be for the better:
- The EMIR fits files will now have only one extension. The second one, which was intended for the variances of each pixel of the detector, is therefore suppressed as, at the detector level, it always results in a constant or predictable value from the value of the signal in the pixel. In this way, the size of the fits files is reduced by half.
- It is included in the TELPOS keyword, which already existed, the options NOD_A / NOD_B that indicate, in the STARE_SPECTRA mode, the nodding position of the telescope. This can be obtained from the IMGOBBL counter, also in the keywords, as well which is set to 1 or 4 for the A, and to 2 or 3 for the B.
October 2018
Subject: EMIR RAMPS improvement
Dear colleagues,
If you have already had the opportunity of getting data from EMIR before the end of September 2017, you may have noticed excessive noise in the preprocessed data frames, together with jumps in the signal throughout the data series, which in some cases are severely hampering the overall performance of the instrument. This is especially important when observing faint sources in spectroscopic mode.
Just for clarification, preprocessed files are those output by the EMIR Control System (ECS) derived from the raw data frames. In the frame list, these are the files without the suffix 'raw' in the name. For CDS read mode, they are calculated by subtracting the second read from the first in each sequence, while for the RAMP mode, they contain the fitted slope to the raw data in each sequence multiplied by the integration time of the sequence. These files are the starting point of the subsequent data reduction and are the ones ingested by the EMIR DRP, both online and offline.
From the very beginning, the EMIR team have been concerned with the noise and lack of stability in the detector data frames and have tried several methods to alleviate these problems. In the course of this work, we recently discovered that the procedure implemented in the ECS to remove the Dark Current and fix the instabilities in the detector data series has not been properly applied. The purpose of this note is to instruct users on how to recover the correction in their EMIR data.
First of all, it is important to note that the flaw is only present in the data taken in RAMP readout mode. Data taken with the CDS mode are unaffected by this. Please check in the corresponding keyword of your fits file, READMODE, to get the read mode of the data before applying the correction method. Second, the gain will be more noticeable in dark areas of the detector, registering only low signal (in between sky lines, outside the target spectra, faint spectrum signal, low background, etc.), so if the data contain bright sources, this correction may not be needed.
Fortunately, the calibration method has been applied properly to the raw frames, which are safely stored on disk, while to derive the slope of each ramp, ECS has incorrectly used the original raw frames, without calibration. The correction consists in reprocessing the raw data frame series to derive the new preprocessed files, from which the reduction should start. To this end, a simple python script (fitramp_ecs.py) that performs this method is available here, and detailed instructions on how to use it are described here.Needless to say, the raw data set has to be at hand before going ahead with this method. If this is not the case, you must contact with the GTC team to get it.
This correction is automatically implemented from 1 October 2018 onwards, hence for data taken after that date this procedure is not strictly needed.
In any case, it is always possible to enhance very low signal to noise data by using different approaches to the ramp calculation. In order to give this possibility to the user, from S19A onwards GTC will provide all the raw data files to EMIR users.
For more details, users are strongly recommended to visit the EMIR Observing Utilities Section available at IAC EMIR website.
February 2017
Subject: EMIR Science Verification Update II
The Science Verification (SV) campaign of EMIR started on January 6th 2017 and we are pleased to announce that one of the imaging programs was already completed. We are making a good progress with the programs requesting long-slit spectroscopy as well. We would like to reiterate that the SV phase is equally important for the demonstration of the scientific capabilities of the new instrument and for the optimization of the observational procedures and training of personal as well. Naturally the efficiency of these early observations is going to be inferior compared to the regular scientific operations. The SV PIs should be aware that we are working hard to acquire their data as soon as possible and of the highest quality (according to our current understanding of the instrument). They will be informed promptly when particular observations are completed. Also bare in mind our requirement for quick feedback on the data and the results from its reduction.
January 2017
Subject: EMIR Science Verification Update
The EMIR team at GTC and the PIs of the approved Science Verification (SV) programs have started to advance on this important milestone of the instrument commissioning. Stay tuned for more exciting news!
December 2016
Subject: Happy Holidays from the EMIR team.
The EMIR team wishes you Happy Holidays and a great New Year 2017 with a "Christmas tree" formed by the CSU (Configurable slit Unit) and a J band image of the NGC6946 galaxy in the background, both acquired with the instrument during the commissioning runs.
June 2016
Subject: EMIR arrives at the GTC!!
The Infrared Multi-Object Spectrograph EMIR, has arrived to its permanent home at the Gran Telescopio Canarias. It was installed at the Naysmith A focal station and is being prepared for the instrument commissioning, science verification and ultimately routine science operations.
The following pictures shows the instrument during the installation process.
August 2014
Subject: EMIR last steps!!
GTC's future work-horse instrument, the Infrared Multi-Object Spectrograph also known as EMIR, is completing its integration tests at the workshops of the Instituto de Astrofísica de Canarias where the instrument has been developed. Tests have been performed at different integration stages under cryogenic conditions, following a precise guideline to ensure the complete functionality of the instrument by the moment to be shipped to la Palma on Summer 2015. The full acceptance plan test is currently being developed by the instrument team, and the formal acceptation of the instrument is expected to be produced on early 2015.
The following picture shows the instrument at IAC workshop, during the comprehensive tests performed in the preparation for the acceptance tests
Although it will still take some time before EMIR will be delivering science routinely at the telescope, the expectations for the instrument are very high. Its combination of imaging and spectroscopic capability, in particular its multi-object mode, make the instrument extremely versatile and powerful, and therefore much sought after.
Last modified: 12 November 2024
