Data Set Overview : This data set contains binned and splined data obtained from the Viking Meteorology Instrument System (VMIS) through most of the Viking Lander 2 mission and the early days of the Lander 1 mission. The data set consists of mean values of pressure, temperature, and wind speed (zonal, meridional, and combined) and relevant statistics and warning flags calculated for 25 bins of equal duration per day. The effect of Lander interference on the temperature measurements is also estimated. The data are presented on a bin by bin basis for Lander 1 sol (Mars solar day after landing) 1-45 and for Lander 2 sol 1-1050 (with the only major gap occurring between sol 561 and 625). Failure of the quadrant sensor on Lander 1 sol 45 (see HESS_ETAL_1977) precludes unambiguous determination of wind direction without modification to the analysis techniques and software used to generate this data set (see HESS_ETAL_1977); therefore, this data set does not include Lander 1 measurements made after sol 45. A data set which has recovered a period of measurements made between Lander 1 sol 1 and 350 is available; refer to PDS data set id VL1-M-MET-4-BINNED-P-T-V-CORR-V1.0.  The 1/25 of a day temporal resolution of this data set make it useful for studies of atmospheric motions, periodicities of oscillations, and diurnal variations in atmospheric properties, among others.. For further background information on the VMIS and results from this experiment, see CHAMBERLAIN_ETAL1976, HESS_ETAL_1977, TILLMAN_ETAL_1979, BARNES_1980, HESS_ETAL_1980, LEOVY_1981, SHARMAN_RYAN_1981, and TILLMAN_1988.  To assist in the utilization of these data, research users are requested to notify James E. Tillman (the data set producer) of their use and applications for these data. Resources permitting, he will communicate any warnings which may be applications dependent, and provide any necessary related documentation. Please address inquiries to:  James E. Tillman Department of Atmospheric Sciences, AK-40 University of Washington Seattle, WA 98195 Telephone: 206-543-4586 NASAMAIL: JTILLMAN  This data set is composed of the following fields (listed as the field name followed by a description):  SC_ID Spacecraft id  SOL_LON Areocentric longitude of the Sun (Ls), derived for the local time corresponding to the beginning of each bin  VIKING_YEAR Viking mission year, starting at 1 when the Viking spacecraft reached Mars, and incremented at Ls : 0 every martian year  MARTIAN_DAY The martian solar day (sol), starting at day 0 when each Lander touched down  LOCAL HR_BIN The hour bin number, starting with 0 at local midnight and incremented by 1 every 1/25 of a martian day  PRESS_MEAN The mean recalibrated atmospheric pressure in each bin  PRESS_TOT The number of recalibrated pressure measurements in each bin  PRESS_FLAG Warning flags concerning binned pressure values with missing data, no data, lander interference, and splined values  ZON_WND_MEAN The mean zonal component of wind speed in each bin  ZON_WND_DEV The standard deviation of the zonal component of wind speed in each bin  MER_WND_MEAN The mean meridional component of wind speed in each bin  MER_WND_DEV The standard deviation of the meridional component of wind speed in each bin  WND_SPD_MEAN The mean combined wind speed in each bin  WND_SPD_DEV The standard deviation of the combined wind speed in each bin  WND_TEM_TOT The number of wind measurements in each bin  WND_TMP_NLI The number of wind measurements in each bin not suffering from Lander interference  WIND_FLG Warning flags concerning binned wind values with missing data, no data, lander interference, and splined values  TAMB_NLI_MN The mean ambient temperature in each bin (No Lander interference experienced)  TAMB_NLI_DEV The standard deviation of the ambient temperature in each bin (no Lander interference experienced)  TREF_NLI_MN The mean reference temperature in each bin (No Lander interference experienced)  TREF_NLI_DEV The standard deviation of the reference temperature in each bin (no Lander interference experienced)  T_NLI_FLAG Warning flags concerning binned temperature values (no Lander interference) with missing data, no data, and splined values  TAMB_INT_MN The mean Lander interference effect on the ambient temperature in each bin  TAMB_INT_DEV The standard deviation of Lander interference effect on the ambient temperature in each bin  TREF_INT_MN The mean Lander interference effect on the reference temperature in each bin  TREF_INT_DEV The standard deviation of Lander interference effect on the reference temperature in each bin  T_INT_FLAG Warning flags concerning Lander interference effects on temperature values with missing data, no data, and splined values   Processing Level Id : 4 Software Flag : Y Processing Start Time : UNK Processing Stop Time : UNK Native Start Time : 97.2 AREOCENTRIC SOL LON, EARTH YR 1976 Native Start Time : 342.0 AREOCENTRIC SOL LON, EARTH YR 1979   Parameters :  Data Set Parameter 'ATMOSPHERIC PRESSURE' ----------------------------------------- The force per unit area exerted by an atmosphere, measured in millibars (10**3 dyne cm**-2).  Data Set Parameter Name : ATMOSPHERIC PRESSURE Data Set Parameter Unit : MILLIBAR Sampling Parameter Name : TIME Sampling Parameter Unit : MARS SOLAR DAY / 25 Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1 Sampling Parameter Interval : 1 Minimum Available Sampling Int : 1 Noise Level : N/A   Data Set Parameter 'TEMPERATURE' -------------------------------- The temperature of a system is a measure of the heat content of the system, and determines if a system is in thermal equilibrium with other systems.  Data Set Parameter Name : TEMPERATURE Data Set Parameter Unit : DEGREES CELSIUS Sampling Parameter Name : TIME Sampling Parameter Unit : MARS SOLAR DAY / 25 Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1 Sampling Parameter Interval : 1 Minimum Available Sampling Int : 1 Noise Level : N/A   Data Set Parameter 'WIND VELOCITY' ---------------------------------- The velocity of a parcel of atmosphere in motion relative to a reference location.  Data Set Parameter Name : WIND VELOCITY Data Set Parameter Unit : METERS/SECOND Sampling Parameter Name : TIME Sampling Parameter Unit : MARS SOLAR DAY / 25 Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1 Sampling Parameter Interval : 1 Minimum Available Sampling Int : 1 Noise Level : N/A   Source Instrument Parameters : Instrument Host ID : VL1 Data Set Parameter Name : TEMPERATURE Instrument Parameter Name : TEMPERATURE Important Instrument Parameters : 1  Instrument Host ID : VL2 Data Set Parameter Name : TEMPERATURE Instrument Parameter Name : TEMPERATURE Important Instrument Parameters : 1  Instrument Host ID : VL1 Data Set Parameter Name : WIND VELOCITY Instrument Parameter Name : TEMPERATURE Important Instrument Parameters : 1  Instrument Host ID : VL2 Data Set Parameter Name : WIND VELOCITY Instrument Parameter Name : TEMPERATURE Important Instrument Parameters : 1  Instrument Host ID : VL1 Data Set Parameter Name : ATMOSPHERIC PRESSURE Instrument Parameter Name : PRESSURE Important Instrument Parameters : 1  Instrument Host ID : VL2 Data Set Parameter Name : ATMOSPHERIC PRESSURE Instrument Parameter Name : PRESSURE Important Instrument Parameters : 1   Processing :  Processing History ------------------ Source Data Set ID : N/A Software : UNK Product Data Set ID : VL1/VL2-M-MET-4-BINNED-P-T-V-V1.0

Overview : The pressure transducers were calibrated to approximately 0.01 to 0.02 millibars accuracy over the ranges expected for martian atmospheric pressure variation. Calibrations to accuracies greater than allowed by the digitizing system were accomplished by test support instrumentation. Repeatability from year to year of the daily average pressures indicates that the transducers have remained stable to significantly better than 0.04 millibars throughout the mission, possibly maintaining stabilities on the order of 0.01 millibars. Due to the binned nature of this data set, accuracy is not limited by the pressure digitization.  The ambient temperature sensor consists of three thermocouples wired in parallel. It is capable of measuring over the entire range of expected martian temperatures with an accuracy of about 1.5 degrees Celsius. Problems with this sensor on Lander 2 were noted shortly before launch. The readings exhibited a temperature-dependent error, increasing as Lander body temperature decreased. The error gradually decreased after power-up of the electronics, approaching a steady-state value after 30-40 minutes of operation. Analysis of the landed data and comparison with the reference temperature sensors on both Landers (see below) and the ambient temperature sensor on Lander 1 permitted a suitable correction to be applied. This required that power be left on continuously to eliminate drift. This was done from Lander 2 sol 25 onward. The corrections to the Lander 2 ambient temperature sensor limit its accuracy to about 3 degrees Celsius (see HESS_ETAL_1977).  The reference temperature sensor was a platinum resistance thermometer mounted between the wind speed elements (see below). It was susceptible to radiation and conduction errors and the effects of the thermal plume of the wind sensor assembly, but corrections for these have been applied. The residual error is believed to be less than 4 degrees Celsius.(see HESS_ETAL_1977).  Wind speed is measured by means of two hot film anemometers oriented orthogonal to each other and lying in the horizontal plane. These hot film elements were maintained at a nominal overheat temperature of 100 degrees Celsius above the air temperature measured by the reference temperature sensor. The power required to maintain each anemometer at the specified temperature was a function of the component of the wind speed orthogonal to the element. Wind speed accuracy is about 10% over most of the range (about 2-150 meters per second) but degrades somewhat for very light winds. Lander interference, ie, wind flowing over the lander, also degrades accuracy; ground testing indicates that the degradation should not be much in excess of 10% for the system as a whole.  The wind speed sensors also measure wind direction, but with a fourfold ambiguity. Selection of the proper quadrant is accomplished by a quadrant sensor, consisting of a heated cylindrical platinum core (maintained at a 100 degrees Celsius overheat) surrounded by four thermocouple junctions at equal angles and distance from the core. Thermocouples on opposite sides of the post comprised a thermocouple pair which was connected in series, allowing for measurement of the temperature differences across each pair. These differences resulted from the thermal wake in the lee of the heated center core. The quadrant sensor values were functions, though not single-valued, of wind speed. The redundant wind speed and directional information provided by both the wind speed and quadrant sensors was combined using a least squares technique to give the best estimates of wind speed and direction. Overall accuracy in wind direction measurement is about 10%.  Failure of the quadrant sensor on Lander 1 sol 45 (see HESS_ETAL_1977) precludes unambiguous determination of wind direction without modification to the analysis techniques and software used to generate this data set (see HESS_ETAL_1977); therefore, this data set does not include Lander 1 measurements made after sol 45. A data set which has recovered a period of measurements made between Lander 1 sol 1 and 350 is available; refer to PDS data set id VL1-M-MET-4-BINNED-P-T-V-CORR-V1.0.  The data set contains the following fields related to confidence level (listed as the field name followed by a  PRESS_FLAG Warning flags concerning binned pressure values with missing data, no data, lander interference, and splined values  WIND_FLG Warning flags concerning binned wind values with missing data, no data, lander interference, and splined values  T_NLI_FLAG Warning flags concerning binned temperature values (no Lander interference) with missing data, no data, and splined values  TAMB_INT_MN The mean Lander interference effect on the ambient temperature in each bin  TAMB_INT_DEV The standard deviation of Lander interference effect on the ambient temperature in each bin  TREF_INT_MN The mean Lander interference effect on the reference temperature in each bin  TREF_INT_DEV The standard deviation of Lander interference effect on the reference temperature in each bin  T_INT_FLAG Warning flags concerning Lander interference effects on temperature values with missing data, no data, and splined values