2.3.2 spase://NASA/NumericalData/ICON/MIGHTI/L2/B/Temperature/PT30S ICON Michelson Interferometer for Global High-resolution Thermospheric Imaging Viewing Direction B Temperature MIGHTI B Temperature 2021-01-01T00:00:00Z MIGHTI samples the O2 A band spectral region at five different wavelengths in order to both measure the shape of the band and to specify a background radiance that is subtracted from the signal. The wavelengths of the filter passbands are selected to maximize the sensitivity to lower thermospheric temperature variations. The temperature measurement is accomplished by a multichannel photometric measurement of the spectral shape of the molecular oxygen A-band around 762 nm wavelength. For each field of view, the signals of the two oxygen lines and the A-band are detected on different regions of a single, cooled, frame transfer charge coupled device (CCD) detector. Two filter channels sample either end of the band to define a background (754.1 nm and 780.1 nm) and three more sample its shape (760.0 nm, 762.8 nm and 765.2 nm). Using three filters that sample the band shape allows the simultaneous retrieval of the atmospheric temperature and common shifts in the center wavelengths of the pass bands due to thermal drifts of the filters. On-board calibration sources are used to periodically quantify thermal drifts, simultaneously with observing the atmosphere. National Aeronautics and Space Administration; Dr. Christoph Englert; Dr. Thomas Immel; See http://icon.ssl.berkeley.edu/Data National Aeronautics and Space Administration Explorers Program contracts NNG12FA45C and NNG12FA42I spase://SMWG/Person/Christoph.Englert PrincipalInvestigator Additional information on ICON https://icon.ssl.berkeley.edu/ ICON spacecraft Homepage. Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI): instrument design and calibration https://doi.org/10.1007/s11214-017-0358-4 Space Science Reviews, 212(1-2), pp.553-584. DOI: 10.1007/s11214-017-0358-4 spase://SMWG/Repository/NASA/GSFC/SPDF Online Open FTPS from SPDF (not with most browsers) ftps://spdf.gsfc.nasa.gov/pub/data/icon/l2/ FTPS access to ICON data via ftps at the Space Physics Data Facility (SPDF) HTTPS from SPDF https://spdf.gsfc.nasa.gov/pub/data/icon/l2/ HTTPS access to ICON data at the Space Physics Data Facility (SPDF) NetCDF Calibrated ICON MIGHTI team spase://SMWG/Instrument/ICON/MIGHTI Dopplergram 2019-12-06T00:00:00Z -P2M PT30S Earth.NearSurface.Atmosphere Earth.NearSurface.Ionosphere Epoch time Epoch This variable contains the time corresponding to the temperature profiles reported in this file. The variable is in milliseconds since 1970-01-01 00:00:00 UTC at middle of image integration. A human-readable version of the time can be found in the variable ICON_...UTC_Time. PT30S ms 0 6000000000000 6000000000000 Magnitude Temporal Bad Calibration File Flag ICON_L1_MIGHTI_B_Quality_Flag_Bad_Calibration Quality Flag indicating an inappropriate calibration file has been used or was missing. PT30S 0 1 -9999999848243207295109594873856 Scalar DataQuality South Atlantic Anomaly Flag ICON_L1_MIGHTI_B_Quality_Flag_South_Atlantic_Anomaly Quality Flag indicating that the spacecraft is within the South Atlantic Anomaly (0 = not in SAA). PT30S 0 1 -9999999848243207295109594873856 Scalar DataQuality A Band Intensity Scaled ICON_L23_MIGHTI_B_ABand_Intensity_Scaled Derived common scaling of O2 A Band radiances in the 3 signal channels by altitude. Calculated forward radiances are fit to the observations from each of the three signal channels. The scaling is done at each tangent altitude separately and interatively until a best fit solution is found. The intensity of each signal channel relative to the other two determines the temperature, so the scale factor is unitless. The scaling is derived using pre-calculated spectra from the HITRAN 2016 database. PT30S -9999999848243207295109594873856 9999999848243207295109594873856 -9999999848243207295109594873856 Scalar Other Uncertainty (1-sigma) in A Band Intensity Scaled ICON_L23_MIGHTI_B_ABand_Intensity_Scaled_Uncertainty Derived uncertainty (1-sigma) in derived common scaling of O2 A Band to emergent intensity by altitude. PT30S 0 9999999848243207295109594873856 -9999999848243207295109594873856 Scalar Other Background Signal per filter ICON_L23_MIGHTI_B_Background_Signal Background Signal by filter by altitude and filter. This has been corrected for flatfield effects across the detector. PT30S Electrons -9999999848243207295109594873856 9999999848243207295109594873856 -9999999848243207295109594873856 Electron Scalar Counts Background Slope ICON_L23_MIGHTI_B_Background_Slope Derived slope of subtracted background. The slope of the background is saved here for diagnostic purposes. It is calculated by taking the difference of the flatfielded signal from the two background channels and dividing by the difference of the the channel center wavelengths (in nm) of the two background channels (approximately 780 nm - 754 nm). This is done explicitly by [bg2 - bg1]/flatfield/[wavelength2 - wavelength1], where bg2 and bg1 are the observed background signals in electrons. PT30S /nm 0 9999999848243207295109594873856 -9999999848243207295109594873856 Photon Scalar Wavelength Total boresight to sun angle ICON_L23_MIGHTI_B_Boresight_Sun_Angle Total boresight to sun angle. PT30S degrees 0 180 -9999999848243207295109594873856 Direction Positional Field of View Azimuth ICON_L23_MIGHTI_B_Field_of_View_Azimuth_Angle Field of view azimuth angle. PT30S degrees -90 90 -9999999848243207295109594873856 Direction Positional Filter Center Wavelength ICON_L23_MIGHTI_B_Filter_Center_Wavelength Filter Center Wavelength used in temperature retrieval (=1e7/FilterCWN). PT30S nm 750 785 -9999999848243207295109594873856 Photon Scalar Wavelength Filter Center Number ICON_L23_MIGHTI_B_Filter_Center_Wavenumber Filter Center Wavenumber used in temperature retrieval as measured in the laboratory and fitted by a Gaussian. These filter center wavenumbers vary with detector (MIGHTI A and MIGHTI B), with altitude as well as with channel. They are also difference for daytime and nighttime operations. It is from these center wavenumbers that the common wavenumber shift (across all channels) is calculated. PT30S cm^-1 12739 13333 -9999999848243207295109594873856 Scalar Other Filter Wavelength Labels ICON_L23_MIGHTI_B_Filter_Wavelengths Wavelength labels corresponding to the five filters. These are for guidance. Actual values used in retrieval for MIGHTI-A and MIGHTI-B (day/night) are in ICON_L23_MIGHTI_(A or B)_Filter_Center_Wavelength. PT30S Scalar Other Filter wavenumber shift ICON_L23_MIGHTI_B_Filter_Wavenumber_Shift Common shift of all filter center wavenumbers due to thermal drift that is added to laboratory measured filter center wavenumbers. The three channels measuring the A band overdetermines the temperature such that the wavenumber registration due to any thermal drift of the instrument can be additionally inferred. This is typically fixed with altitude and determined (along with temperature) from the signal originating from the O2 A band as measured from 3 signal channels. PT30S cm^-1 -9999999848243207295109594873856 9999999848243207295109594873856 -9999999848243207295109594873856 Scalar Other Filter wavenumber shift uncertainty ICON_L23_MIGHTI_B_Filter_Wavenumber_Shift_Uncertainty Uncertainties (1-sigma) in the shift of all filter center wavenumbers. If the common wavenumber shift is fixed with altitude and prescribed, then this uncertainty is zero everywhere. PT30S cm^-1 0 9999999848243207295109594873856 -9999999848243207295109594873856 Scalar Other GPS Time ICON_L23_MIGHTI_B_GPS_Time Milliseconds since 1980-01-06 00:00:00 TAI (coincident with UTC) at middle of image integration. Derived from original GPS values reported from spacecraft (Time_GPS_Seconds and Time_GPS_Subseconds). Time calculation is offset by 615ms (flush time) for the first image in the series and for all other images are adjusted by subtracting (integration time + 308 milliseconds) from the reported GPS time. PT30S ms -9223372036854775806 Magnitude Temporal GPS seconds count when image packet header received ICON_L23_MIGHTI_B_GPS_Time_Seconds The header of the first image received in a series 615 ms after start of image processing. Following headers are adjusted by subtracting (integration time + 308 ms) from the reported GPS time. PT30S seconds -9223372036854775806 Magnitude Temporal Clock GPS Time Offset ICON_L23_MIGHTI_B_GPS_Time_Subseconds GPS Time in sub seconds, 50 nanosecond offset from GPS seconds from 20 MHz clock. PT30S 50 Nanoseconds 0 100000000 -9223372036854775806 Magnitude Temporal Time to integrate MIGHTI-B region of interest (ROI) image. ICON_L23_MIGHTI_B_Integration_Time MIGHTI Integration Time in millieconds. PT30S ms 0 4294967294 -9223372036854775806 Magnitude Temporal Relative Radiance per Filter ICON_L23_MIGHTI_B_Relative_Radiance Observed relative radiance by filter and altitude. The retrieval is based on a forward modeling approach to these observed radiances as reported in electrons/s from the MIGHTI L1 product. These are converted to electrons based on the integration time during day (30 s) or night (60 s). PT30S Electrons 0 9999999848243207295109594873856 -9999999848243207295109594873856 Electron Scalar Counts Uncertainty in Rel Radiance per filter ICON_L23_MIGHTI_B_Relative_Radiance_Uncertainty Uncertainty (1-sigma) in relative radiance by filter by altitude and filter. These are calculated by taking the square root of the total number of electrons in each of the three signal channels, which are 51 pixels wide for MIGHTI-A or MIGHTI-B (day or night). PT30S Electrons 0 9999999848243207295109594873856 -9999999848243207295109594873856 Electron Uncertainty Counts Tangent Altitude of the Line of Sight ICON_L23_MIGHTI_B_Tangent_Altitude Tangent point altitudes. These altitudes are the tangent altitude of the line of sight of each pixel. PT30S km 100 9999999848243207295109594873856 -9999999848243207295109594873856 Direction Positional Tangent Point Latitudes by Altitude. ICON_L23_MIGHTI_B_Tangent_Latitude Tangent point latitudes by altitude. Note that these are a function of both epoch and altitude. Note also that due to the nature of the limb observations these latitudes are typically an average over many hundreds of kilometers. PT30S deg -90 90 -9999999848243207295109594873856 Direction Positional Local Solar Time at Tangent Point ICON_L23_MIGHTI_B_Tangent_Local_Solar_Time Local solar time (0-24 h) at tangent point calculated using the equation of time. LST is a function of both epoch and altitude. PT30S hours 0 24 -9999999848243207295109594873856 Direction Positional Tangent Point Longitudes by Altitude. ICON_L23_MIGHTI_B_Tangent_Longitude Tangent point longitudes (0-360) by altitude. Note that these are a function of both epoch and altitude. Note also that due to the nature of the limb observations these longitudes are typically an average over many hundreds of kilometers. PT30S deg 0 9999999848243207295109594873856 -9999999848243207295109594873856 Direction Positional Tangent Point Magnetic Latitudes by Altitude. ICON_L23_MIGHTI_B_Tangent_Magnetic_Latitude Tangent point magnetic latitudes by altitude. Quasi-dipole latitude and longitude are calculated using the fast implementation developed by Emmert et al. (2010, doi:10.1029/2010JA015326) and the Python wrapper apexpy (doi.org/10.5281/zenodo.1214207). Quasi-dipole longitude is defined such that zero occurs where the geodetic longitude is near 285 deg east (depending on latitude). Note that these are a function of both epoch and altitude. Note also that due to the nature of the limb observations these latitudes are typically an average over many hundreds of kilometers. PT30S deg -90 90 -9999999848243207295109594873856 Direction Positional Tangent Point Magnetic Longitudes by Altitude. ICON_L23_MIGHTI_B_Tangent_Magnetic_Longitude Tangent point magnetic longitudes by altitude. Quasi-dipole latitude and longitude are calculated using the fast implementation developed by Emmert et al. (2010, doi:10.1029/2010JA015326) and the Python wrapper apexpy (doi.org/10.5281/zenodo.1214207). Quasi-dipole longitude is defined such that zero occurs where the geodetic longitude is near 285 deg east (depending on latitude). Note that these are a function of both epoch and altitude. Note also that due to the nature of the limb observations these longitudes are typically an average over many hundreds of kilometers. PT30S deg 0 9999999848243207295109594873856 -9999999848243207295109594873856 Direction Positional Solar Zenith Angle at Tangent Point ICON_L23_MIGHTI_B_Tangent_Solar_Zenith_Angle Solar zenith angle at tangent point. SZA is a function of both epoch and altitude. PT30S degrees -180 180 -9999999848243207295109594873856 Direction Positional A-Band Temperatures ICON_L23_MIGHTI_B_Temperature Derived temperatures from A band by altitude. Temperatures are retrieved from the rotational distribution of emission lines in the O2 A band. The measurement is made at 5 spectral channels. 3 channels measure the A band and 2 others on either side of the band measure a background, which is subtracted from the 3 signal channels. An entire altitude profile is observed simultaneously. An onion-peeling inversion is used on the raw observations to remove the effects of the integration along the line of sight. See Stevens et al. (Space Science Reviews (2018) 214:4. https://doi.org/10.1007/s11214-017-0434-9). O2 A band spectra are pre-calculated from 100-400 K in 20 K increments based on the HITRAN 2016 database [Gordon et al., JQSRT (2017), 203:3-69.https://doi.org/10.1016/j.jqsrt.06.038] and smoothed filter functions with FWHM of ~2.0 nm. The filter functions are based on Gaussian fits to laboratory measurements and are a function of channel, row (altitude), and column. The fits are separately done for each pixel as a function of peak wavenumber (wavelength), width, and transmittance. For each of the three signal channels the fitted Gaussians are co-added over 51 pixels where the transmittance is largest for a representative filter function for that channel. The transmittances are not absolutely calibrated in photometric units, but the relative transmittance between channels and between detectors is maintained, which allows for the retrieval of temperature at the tangent altitude. PT30S K 0 9999999848243207295109594873856 -9999999848243207295109594873856 Molecule Scalar Temperature 16 Temperature Bias Uncertainties ICON_L23_MIGHTI_B_Temperature_Bias_Uncertainty Estimated bias uncertainties in derived temperatures by altitude; aka systematic uncertainties. These uncertainties are present in each temperature profile and are primarily due to 1) a 1 cm-1 uncertainty in the common shift applied to pre-flight laboratory determined filter positions. This uncertainty was tested in the retrieval and a derived fixed uncertainty of 12 K is propagated at all altitudes and 2) the lack of measurements above the top altitude sampled, and altitude dependent, with the topmost altitudes of the retrieval affected the most. The temperature bias uncertainty is found by a root sum square of these two. At most altitudes the estimated bias uncertainty is dominated by the uncertainty in the common shift. PT30S K 0 9999999848243207295109594873856 -9999999848243207295109594873856 Molecule Uncertainty Temperature 16 Temperature Statistical Uncertainties ICON_L23_MIGHTI_B_Temperature_Statistical_Uncertainty Statistical uncertainties (one sigma) in derived temperatures by altitude. PT30S K 0 9999999848243207295109594873856 -9999999848243207295109594873856 Molecule Uncertainty Temperature 16 Total Uncertainties in Derived Temperatures by Altitude ICON_L23_MIGHTI_B_Temperature_Total_Uncertainty Total uncertainties in derived temperatures by altitude: Here the statistical temperature uncertainty has been linearly added to the estimated temperature bias. PT30S K 0 9999999848243207295109594873856 -9999999848243207295109594873856 Molecule Uncertainty Temperature 16 Thermal Electric Cooler Cold Temperature ICON_L23_MIGHTI_B_Thermal_Electric_Cooler_Cold_Temperature Cold-side temperature of the thermoelectric cooler attached to the camera head. PT30S C -9999999848243207295109594873856 9999999848243207295109594873856 -9999999848243207295109594873856 Scalar InstrumentMode UTC time ICON_L23_MIGHTI_B_UTC_Time This variable is the same as Epoch but is formatted as a human-readable string. PT30S ' ' -9999999848243207295109594873856 Magnitude Temporal UTC Start time ICON_L23_MIGHTI_B_UTC_Time_Start Milliseconds since 1970-01-01 00:00:00 UTC at start of image integration. Derived from original GPS values reported from spacecraft (Time_GPS_Seconds and Time_GPS_Subseconds). Time calculation is offset by 615ms (flush time) for the first image in the series and for all other images are adjusted by subtracting (integration time + 308 milliseconds) from the reported GPS time. PT30S ' ' -9999999848243207295109594873856 Magnitude Temporal UTC Stop time ICON_L23_MIGHTI_B_UTC_Time_Stop Milliseconds since 1970-01-01 00:00:00 UTC at end of image integration. Derived from original GPS values reported from spacecraft (Time_GPS_Seconds and Time_GPS_Subseconds). Time calculation is offset by 615ms (flush time) for the first image in the series and for all other images are adjusted by subtracting (integration time + 308 milliseconds) from the reported GPS time. PT30S ' ' -9999999848243207295109594873856 Magnitude Temporal MIGHTI-B Aperture Position 1 ICON_L23_MIGHTI_Aperture_1_Position Aperture Position 1: 0=OPEN, 1=CLOSED, 2=15% OPEN, 3=UNKNOWN. Note that when OPEN (0) the integration time is 60 s for nighttime observations and when 15% OPEN (2) the integration time is 30 s for daytime observations. PT30S ' ' 0 3 -9999999848243207295109594873856 Scalar InstrumentMode MIGHTI-B Aperture Position 2 ICON_L23_MIGHTI_Aperture_2_Position Aperture Position 2: 0=OPEN, 1=CLOSED, 2=15% OPEN, 3=UNKNOWN. Note that when OPEN (0) the integration time is 60 s for nighttime observations and when 15% OPEN (2) the integration time is 30 s for daytime observations. PT30S ' ' 0 3 -9999999848243207295109594873856 Scalar InstrumentMode Altitude of the ICON Spacecraft ICON_L23_Observatory_Altitude Spacecraft altitude at middle of exposure. PT30S km 0 9999999848243207295109594873856 -9999999848243207295109594873856 Direction Positional Latitude of the ICON Spacecraft ICON_L23_Observatory_Latitude Spacecraft latitude at middle of exposure. PT30S deg -90 90 -9999999848243207295109594873856 Direction Positional Local Solar Time of the ICON Spacecraft ICON_L23_Observatory_Local_Solar_Time Spacecraft local solar time (0-24) at middle of exposure. PT30S deg 0 24 -9999999848243207295109594873856 Direction Positional Longitude of the ICON Spacecraft ICON_L23_Observatory_Longitude Spacecraft longitude (0-360) at middle of exposure. PT30S deg 0 360 -9999999848243207295109594873856 Direction Positional Solar Zenith Angle of the ICON Spacecraft ICON_L23_Observatory_Solar_Zenith_Angle Spacecraft solar zenith angle at middle of exposure. PT30S deg -180 180 -9999999848243207295109594873856 Direction Positional Orbit Node Flag ICON_L23_Orbit_Node Flag indicating that the spacecraft is ascending (0) or descending (1) node. PT30S 0 1 -127 Scalar Orientation Orbit Number ICON_L23_Orbit_Number Orbit Number PT30S 0 105000 -999 Scalar Temporal