System Verification Principles

The three phases of System Verification
The System Verification teams
Observing modes
Timing of SV and availability of SV data

1. The Three Phases of System Verification

System Verification activities can be classified into three broad areas: Observation Definition, Observation Execution, and Observation Assessment.

The Observation Definition phase includes verifying the tools that the Gemini community will use to define observations on the Gemini Telescopes. These may include some or all of: the Integration Time Calculator (ITC), the Phase I Tool (PIT), the Observing Tool (OT), high-level operation and sequence execution (OCS) and automatic data processing (OLDP).

The ITC calculates the integration time to achieve the specified signal-to-noise ratio from the instrument performance and the seeing and other weather conditions specified by the science program. The performance of the ITC will be verified by comparison of its predictions with the results of the SV observations.

The PIT will be used to prepare proposals for SV observations.

The OT will be used to define the SV observations. The observations will be chosen to demonstrate that the OT has the flexibility and scope to specify observation types of interest, that the process for selection of reference stars for the wavefront sensors functions properly, and that appropriate calibration observations can be defined. In addition, integration of the OT with scheduling tools, schedule reporting, and communications with telescope users will be verified.

The Observation Execution phase will verify the execution of the observations defined by the OT and will exercise the range of observing options to be supported by Gemini. These options will eventually include queue and classically scheduled measurements, remote observations from the base facilities and some partner countries. Calibration observations, quality checking, and data distribution all will be verified and observing overheads will be quantified.

The Observation Assessment phase will demonstrate that the data processing pipeline works properly for each instrument and that data distribution takes place as designed. It also will verify that the instrument capabilities are as advertised, and that baseline calibration procedures produce the information necessary to calibrate the SV data so that scientifically useful measurements result. In addition, it will exercise the user support documentation and support procedures. After verification of their quality during this internal assessment, the SV observational data will be made available to the Gemini community for further assessment and utilization, providing additional feedback to Gemini on issues such as data quality, instrument capabilities, and telescope performance.

2. The System Verification Teams

System Verification activities will be performed by teams led by Gemini scientific staff who will define the SV observations, assure that all preparations are in place, carry out the observations, and provide the assessment of data quality and system performance. The SV teams will include membership from some or all of the following groups as require to complete the SV plan: Gemini scientific staff, members of the instrument team, members of the National Gemini Offices and other scientists from the community. The teams will thus include scientists who are the most knowledgeable of the Gemini Observatory and its instrumentation, and who represent the Gemini partner perspectives. They include the individuals who are in the best position to implement any needed modifications to the telescope and instrument procedures and/or observing tools, if shortcomings are uncovered during the SV process.

The SV plan will be reviewed by the Gemini Science Committee to verify that it meets the goals of SV, and telescope time to execute the SV plan will be assigned by the Director.

System Verification tests will serve as valuable trial runs for Gemini staff and will train staff in instrument and telescope control, data reduction, and in interacting with the Gemini community. They also will provide the Gemini National Office Scientists with firsthand experience in interacting with the Gemini Observatory, a role they will be responsible for supporting in their communities.

3. Observing Modes

System Verification will be performed for each observing mode of an instrument and telescope combination. "Observing mode" is a somewhat loose term describing a discrete type of observation where instrumental parameters such as spectral resolution and field of view, telescope parameters such as chopping and nodding, and/or external parameters such as background radiation, lead to significantly different types of observations. For example, imaging and grism spectroscopy with NIRI constitute two modes of the instrument. SV for each of these modes need not include every filter or wavelength, but surely will include observations in both the thermal (l > 2.5mm) and non-thermal (l < 2.5mm) infrared. Likewise, for GMOS long slit spectroscopy and multi-slit spectroscopy are two different modes requiring two sets of SV observations; one would not assume that because one of them works the other one does as well.

4. Timing of SV and Availability of SV data

For each mode of each instrument, planned observations for system verification (the SV Plan) will be published prior to their execution, as part of the announcement of the first semester of availability of that mode of the instrument. This announcement will also include the expected (but not yet verified) performance of the instrument within the Gemini system.

For each mode of each instrument the SV tests will be undertaken in the final months prior to availability of that mode to the community. SV for each mode of each instrument will be accomplished in no more than two clear nights. Note that as a result of the SV tests, the earlier description of the instrument’s performance may require modification.

In general not every mode of an instrument will be offered initially. Only those modes that have been verified successfully will be made available to the Gemini communities.

In summary, the SV observations will be selected by SV team members and approved by the Gemini Director. They will span a wide range of targets and perspectives and the SV teams will be responsible for providing written, in depth assessments of SV observations and mode verification within three months of data acquisition. The data obtained during SV will be made available by ftp to the international Gemini community and the assessments will be published on the Gemini SV web pages. Community participation in the further evaluation and assessment of the SV observations will help ensure that Gemini instruments are a success from the first date of scheduled observations.

Last update July 20, 2006; Rachel Mason
In original form June 6, 1999; Tom Geballe and Fred Gillett