May 18, 2009
Warm temperatures on the summit have helped push the SPEC temerature higher. Recent operating temperatures have been 72 K, then 73 K, then 74 K, 75 K, and 75.5 K. I will continue taking darks to monitor performance.
April 20, 2009
OSIRIS is usable, but operating warmer than before. Temperatures within the dewar are 8 to 10 K above normal. We have stabilized the SPEC detector to 72 K, 4 K above our nominal 68 K operating temperature. Dark frames look good cosmetically, subtract well, and seem stable over several days. The IMAG detector remains at its nominal 70 K.
Warmer temperature darks are available on our public ftp site.
| Temp (K) | Mean Counts 900s Dark (DN/s) |
Median Counts 900s Dark (DN/s) |
Measurements |
|---|---|---|---|
| 68.0±0.1 | 1.64±0.74E-02 | 1.47E-02 | 208 |
| 72.0±0.1 | 2.08±0.23E-02 | 2.06E-02 | 8 |
| 73.0±0.1 | 2.34±0.21E-02 | 2.30E-02 | 16 |
| 74.0±0.1 | 2.60±0.13E-02 | 2.55E-02 | 29 |
| 75.0±0.1 | 3.15±0.20E-02 | 3.09E-02 | 17 |
| 75.5±0.1 | 3.32±0.19E-02 | 3.29E-02 | 8 |
| 78.0±0.1 | 4.47±0.19E-02 | 4.47E-02 | 8 |
| 79.0±0.1 | 5.45±0.08E-02 | 5.45E-02 | 5 |
| 80.0±0.1 | 6.50±0.14E-02 | 6.53E-02 | 10 |
| 80.0±0.1 | 6.79±0.19E-02 | 6.77E-02 | 26 |
| 83.5±0.1 | 1.28±0.005E-01 | 1.28E-01 | 5 |
| 84.5±0.1 | 1.57±0.01E-01 | 1.57E-01 | 7 |
The wide range for dark current at 68 K is likely due to not selecting data. That is, some darks were taken immediately after the detector was reset, which causes a known noise artifact.
 |
|
| Read Noise using the "2-bias method":
RN = stdev(im1-im2) / sqrt(2) / gain where: im1 and im2 are darks and gain = 0.23 DN/e |
|
 |
 |
| T=73 K Dark | T=72 K Dark |
 |
 |
| T=68 K Dark | |
 |
| Subtraction of 2 T=73 K Darks (same day) | Subtraction of 2 T=72 K Darks (different days) |
 |
 |
| Subtraction T=72 Dark from T=68 K Dark | |
 |
February 20, 2009
OSIRIS has suffered from thermal issues that have caused higher dark current in the SPEC detector. We have also seen images shift when changing plate scales. We have recently completed a service of OSIRIS and reached the following conclusions:
OSIRIS was serviced in February 2009. We think that we have repaired a thermal short, but we were unable to determine a cause of the image motion with changing plate scale. It's possible that the thermal cycle will change the performance of the SPEC image motion. We expect to return OSIRIS to full capability on March 31, 2009.
For more details, please read our Preliminary Report.
May 9, 2008
The following is a email sent to all known OSIRIS users regarding the March 2008 service mission.
Dear OSIRIS users,
There have been significant changes to OSIRIS since March 2008 and we want you to know about the changes. If you have received this email in error, please accept my apologies.
- In early March we serviced OSIRIS to add new K-band filters with built-in pupils for the 100 mas scale. These new filters are called Kcb, Kc3, Kc4, and Kc5 and are identical to the Kbb, Kn3, Kn4, and Kn5 filters respectively. Both sets of K-band filters are in the instrument. To make room for these new filters, we removed the Open, Zn2, Zn3, and Zn5 filters. The new KcX filters are meant to be used only with the 100 mas plate scale. For all other plate scales, please continue to use the original K-band filters. We have engineering time in June to measure the difference in background between the old and new filters. All operational software has been updated to reflect the changes. Observers may wish to download new versions of the Manual, OOPGUI, and DRP from the OSIRIS Toolbox web page.
- During this mission, we fixed a mechanical issue with the OSIRIS handling cart that prevented the instrument from defining in the proper location. Since the mission, we can now measure the focus offset among the 4 SPEC plate scales and the Imager.
- We have developed software to automatically correct for the focus offsets among the 4 SPEC plate scales and the imager. This software is transparent to the observer, but there are important things to note:
- If you are taking simultaneous SPEC and IMAG frames, sky frames will be focused for the imager, object frames will be focused for the spectrograph.
- If you are taking SPEC frames only, object and sky frames will be focused for the SPEC plate scale.
- If you are taking IMAG frames only, object and sky frames will be focused for the Imager.
- We have converted OSIRIS over to use the kvnc suite of software developed for mainland observing. OSIRIS will no longer use the osiris server as its VNC server; rather, it will use svncserver2. The change should be transparent for Waimea observers and mainland observers will no longer have to hand-edit a script to start the proper VNC viewer.
jim
April 28, 2008
OSIRIS will now automatically account for the focus offset among the scales when scripts are run via the GUIs.
April 28, 2008
The OSIRIS Rectification Matrices Webpage has been updated with the new "Kc" filters under the "v4.0" heading. Except for the new "Kc" filters, all other matrices are identical to "v3.0".
April 28, 2008
Links for the OSIRIS Manual and for software on the Tools Page have been updated.
March 7, 2008
OSIRIS was serviced yesterday by Keck and UCLA personnel. We had two goals for the service: investigate and correct the global and relative focus jumps; install new K-band filters for the 100 mas scale.
We found that the OSIRIS handling cart was stopping too far from the AO bench. This seemed to prevent the instrument from defining correctly. We adjusted the switch on the handling cart to allow it to move closer to the AO bench.
Inside the dewar, we found the locking mechanism on the lens barrels for the 35- and 100-mas scales to be loose. Unexpectedly, we found the 50-mas lens barrel to be secure. We tightened the locking mechanism for all scales and adjusted the 50-mas to more closely align to the 20-mas scale, which is our reference point. OSIRIS is still warm so testing has not started.
We removed the Opn, Zn2, Zn3, and Zn5 filters and replaced them with filters equivalent to the Kbb, Kn3, Kn4, and Kn5 filters. These new filters also have 9-m pupils installed that will significantly reduce the background observed in the 100-mas scale. These new filters are named Kcb, Kc3, Kc4, and Kc5, where the 'c' is for coarse. These filters are intended only for the 100 mas scale. Software has been updated and tested.
March 5, 2008
Recent fiber testing with OSIRIS has confirmed that the 4 OSIRIS plate scales are no longer parfocal. This accounts for part of the image quality problems observers have seen in the 50 mas scale. An OSIRIS service mission starts tomorrow which will attempt to correct the problem.| Scale (mas) | Focal shift (mm) |
|---|---|
| 20 | 0 |
| 35 | -0.25 ± 0.25 |
| 50 | -1.75 ± 0.25 |
| 100 | 0 |
August 21, 2007
Recent fiber testing with OSIRIS has confirmed that the 4 OSIRIS plate scales are no longer parfocal. This accounts for part of the image quality problems observers have seen in the 50 mas scale. Most likely, the 2006 earthquake or subsequent service mission caused the focal shift. We are investigating ways to correct or compensate for the focal shift.| Scale (mas) | Focal shift (mm) |
|---|---|
| 20 | 0 |
| 35 | 0.50 ± 0.25 |
| 50 | 1.00 ± 0.25 |
| 100 | 0 |
August 2, 2007
The OSIRIS rectification matrices are now online and available for download.August 1, 2007
Jim Lyke has produced a DRP Cookbook to help users get started in reducing data.July 26, 2007
Recently, we've noticed some image quality issues related to the 50 mas scale of OSIRIS. We are investigating the cause. Possiblities include:- We have an incorrect offset to the center of the 50 mas scale such that we are vignetting the beam slightly.
- There is a focus offset for the 50 mas scale.
- Something on the AO bench changes with OSIRIS spec scale
In a possibly related note, some observers have recently described problems in offsetting from the center of one scale to another. This could indicate an incorrect offset value for the 50 mas scale.
We need the AO bench to investigate this issue. OSIRIS will next be in AO between August 5 - 22, 2007.
June 6, 2007 note to observers from James Larkin
Dear OSIRIS users,
We have just released the latest version of the pipeline, quicklook2, and OSIRIS manual (version 2.0). There have been significant improvements and changes to the pipeline, we highly recommend that all users refer to the manual for your reductions. In addition we have included a new interactive data reduction pipeline gui (ODRFGUI) which allows users to easily operate and generate pipeline files. This new GUI should be run with the latest version of the pipeline (version 2.0). All of this can be downloaded from the
Keck OSIRIS Toolbox or the UCLA OSIRIS webpage.
List of Major Changes to the Pipeline
- Added new module "Correct Dispersion" - corrects for atmospheric dispersion and chromatic dispersion from the AO bench and should be performed on all OSIRIS cubes after "Assemble Data Cube" in the final reduction processes (GUI puts this in the correct order).
- Added a new module "Extract Star" - extracts 1D spectrum of a stellar object from an OSIRIS cube, typically for telluric extraction.
- Added a new module "Remove Hydrogen Lines" - takes a 1-D spectrum and attempts to remove absorption lines due to hydrogen. The primary purpose is to remove hydrogen absorption lines from telluric standard stars before dividing them into science exposures.
- Added a new module "Divide by Blackbody" - divides a 1-d, 2-d or 3-d spectrum by a blackbody of a specified effective temperature (Kelvin). This is primarily useful to fix telluric spectra, and accepts different wavelength ranges.
- Added a new module "Divide by Star Spectrum" - Divides cube by 1-d stellar spectrum. This is primarily useful for telluric correction.
- Fixed wavelength solution to resolve small ~0.1 A shifts between each lenslet wavelength solution.
- The "Mosaic Frames" module now updates the RA and DEC header in the output file when multiple frames are mosaiced together.
Happy Reductions!
Best,
James