Calibrated Data Record (CDR)

Calibrated Data Record (CDR)

The VIRS data cover a wavelength range from 300 to 1050 nm (VIS) and 850-1450 nm (NIR). The VIRS Calibrated Data Records (CDRs) consist of calibrated data derived from MASCS VIRS Experimental Data Records (EDR).

The data span Earth, Venus and Mercury fly-bys and routine orbital observations that began on March 29, 2011.

The CDR archive is arranged according to mission phase: Launch (lau), Earth Cruise (eac), Earth Flyby (eaf), Venus 1 & 2 Cruise (vc 1 & 2), Venus 2 Flyby (vf2), Mercury Cruise 1-4 (mc1-4) , Mercury flyby 1-3 (mf1-3) , Mercury Orbit 1-5 (orb, orb2-5). Then by day, which includes UVVS (UV to visible) and VIRS (visible to IR). Within VIRS the data are subdivided according to VIS and NIR and, within each category, a science and housekeeping file compose an individual data product.

Useful Documents

Useful documents located in the documents directory
VIRS_TUTORIAL.PDF: MASCS VIRS Tutorial/User's Guide in PDF/A format.

VIRS_CDR_DDR_DAP_SIS.PDF: The MASCS VIRS CDR/DDR/DAP SIS: "MESSENGER MASCS VIRS Calibrated Data Record, Derived Data Record, and Derived Analysis Product Software Interface Specification"

VIRS_EDR2CDR.TXT: Detailed procedures and tables for EDR to CDR calibration.

VIRS_CDR2DDR.TXT: Detailed procedures and tables for CDR to DDR data reduction.

MASCS_CAL_RPT.PDF: The MESSENGER instrument calibration report for MASCS, in Adobe Acrobat format.

VIRS_DARK_ANALYSIS_REPORT_1.PDF: "VIRS IR Dark Analysis Report 1: Operational Changes" Details the evolving understanding of MASCS dark current during Mercury orbit, describing temperature dependence and effects on the NIR data in particular.

VIRS_DARK_ANALYSIS_REPORT_2.PDF: "VIRS IR Dark Analysis Report 2: Calibration Changes". Describes the adjustments to MASCS calibration to improve dark subtraction and account for pixels saturated due to temperature.

VIRS_CALIBRATION_CHANGES_PDS9.PDF: "VIRS Calibration Changes for PDS Delivery 9" Describes the calibration changes implemented to simplify the handling of dark subtractions for VIRS, and an adjustment to the DATA_QUALITY_INDEX provided in the data records.

VIRS_CALIBRATION_CHANGES_PDS11.PDF: "VIRS Calibration Changes for PDS Delivery 11" Describes changes to the calibration procedure that have been implemented to remedy an observed shift in the wavelength scale of the VIRS visible channel.

VIRS_FLATFIELD_REPORT.PDF: "MASCS/VIRS Lamp-Based Flat Field Report" Describes the results of an investigation to derive a flat-field correction for the MASCS VIRS surface observations.

Access to the Calibrated Data

The CDRs are in binary format and each product is described by a detached PDS label. The files contain 1 spectrum per row and the corresponding geometry. Range in longitude and latitude, footprint size, incidence and emission angles and phase angle are included. Detailed descriptions of the parameters in the label can be found in the label directory.

See the VIRS Calibrated and Derived Data Record Software Interface Specification Document

Quick Look Indices

Indices for Calibrated data for the Ultraviolet date Specific Mission Phases – Individual files can be selected based on observational parameters and the corresponding URNs submitted below to retrieve the files. These indices contain URN, Start and Stop Times, Sub-Solar Longitude and Latitude, Sub-Spacecraft Longitude and Latitude, Altitude and Phase Angle computed for the Start Time. File size is included. Because the individual files contain varying numbers of spectra, the total observing time included in an individual product varies from under a minute to over 2 hours, limiting the use of these indices. Nevertheless, the parameters can be used to guide initial access to the data.

Selecting Data at the file level

Accessing Binary Files

An IDL tool which translates the CDR binary files is available (See side bar)