ICON The Far Ultra Violet Imaging Spectrograph Day Limb Images

FUV Day Limb Images

https://doi.org/10.48322/BWJZ-NK36

2024-06-05 00:00:00Z

The FUV instrument takes 2D images of the Earth’s horizon in the Far ultraviolet.
The imager is pointing approximately 90 degrees to the spacecraft motion, similar to looking out
of the side window of a car as it drives down the road. Onboard electronics read the CCD detectors 8 times per
second and collect the data into radiance profiles every 12 seconds. The calibrated level 1 radiances
and Level 1 ancillary spacecraft data are combined in a limb retrieval to produce the level 2.4 O/N2 limb product.

National Aeronautics and Space Administration; Dr. Andrew W. Stephan; Dr. Thomas Immel

Online

Open

NetCDF

Please acknowledge Andrew W. Stephan and Robert R. Meier. Please acknowledge the Data Providers and CDAWeb when using these Data.

Online

Open

NetCDF

None

Please acknowledge Andrew W. Stephan and Robert R. Meier. Please acknowledge the Data Providers and CDAWeb when using these Data.

PT12S

Epoch Time

Epoch

Time corresponding to the center of each observation, in milliseconds since Jan 1 1970.

PT12S

ms

0

6000000000000

-999

Altitude Grid Used by the Retrieval

ICON_L24_Altitude

Altitude grid used by the retrieval, in WGS, as a function of time.

PT12S

km

-600

600

-999

Ap Index

ICON_L24_Ap

Value of Ap used in the forward model, as a function of time. These data are from http://www-app3.gfz-potsdam.de/kp_index/. These are the tabulated Kp values from GFZ German Research Centre for Geosciences at the Helmholtz Centre Potsdam.

PT12S

0

400

-999

Retrieved Disk Column O/N2

ICON_L24_Column_O_N2

Retrieved column O/N2 from the limb data, as a function of time.

PT12S

Dimensionless

0

45

-999

F10.7 Used in Inversion Process

ICON_L24_F107

Unscaled value of F10.7 used as an input to the inversion process, as a function of time. These data are from ftp://ftp.seismo.nrcan.gc.ca/spaceweather/solar_flux/fluxtable.txt. These are the solar radio flux values tabulated from the Space Weather Canada which is a part of Natural Resources Canada.

PT12S

sfu

0

500

-999

Tangent Altitudes of Input Data

ICON_L24_Input_Altitude

Tangent altitudes of input data, in km above the WGS-84 geoid, as functions of time.

PT12S

km

-1000

1000

-999

Corrected Input Data for the Long Wave Channel

ICON_L24_Input_Corrected_LW_L1_Radiance

Corrected input data for the long wave channel, in Rayleighs, as functions of tangent altitude and time.

PT12S

Rayleighs

-1000

1000

-999

Corrected input data for the Short Wave Channel

ICON_L24_Input_Corrected_SW_L1_Radiance

Corrected input data for the short wave channel, in Rayleighs, as functions of tangent altitude and time.

PT12S

Rayleighs

-1000

1000

-999

Line of Sight Azimuth Angles

ICON_L24_Input_Look_Azimuth_Angle

Line of sight azimuth angles, in degrees, as functions tangent altitude of time.

PT12S

degrees

-360

360

-999

Line of Sight Zenith Angles

ICON_L24_Input_Look_Zenith_Angle

Line of sight zenith angles, in degrees, as functions tangent altitdue of time.

PT12S

degrees

0

180

-999

Uncorrected Input Data for the Long Wave Channel

ICON_L24_Input_Uncorrected_LW_L1_Radiance

Uncorrected input data for the long wave channel, in Rayleighs, as functions of tangent altitude and time.

PT12S

Rayleighs

-1000

1000

-999

Uncorrected Input Data for the Short Wave Channel

ICON_L24_Input_Uncorrected_SW_L1_Radiance

Uncorrected input data for the short wave channel, in Rayleighs, as functions of tangent altitude and time.

PT12S

Rayleighs

-1000

1000

-999

Data Collection Mode

ICON_L24_Instrument_Mode_Flag

Data collection mode of FUV instrument
1 = Dayside science
2 = Nightside science
3 = Calibration
4 = Nadir
5 = Conjugate
6 = Stars
7 = Ram
8 = Off Target
9 = Engineering
13 = Unknown.

PT12S

0

127

127

Number of Iteration Steps

ICON_L24_Iteration_Steps

Diagnostic Number of iteration steps performed before model converged on answer, as a function of time.

PT12S

0

45

-999

Latitude of the Retrieval

ICON_L24_Latitude

Latitude of the retrieval, defined at 150 km tangent altitude, in WGS.

PT12S

degrees

-90

90

-999

Quality Flag of Data Quality

ICON_L24_Level_1_Quality_Flag

QUALITY_FLAG is an indicator of data quality =
0 = No errors or quality conditions, LVLH
1 = No errors or quality conditions, R-LVLH
2 = Lunar calibration
3 = Insufficient high voltage
4 = Nadir calibration
5 = Zero wind calibration
6 = Bad pointing
7 = S/C attitude slew
8 = Conjugate observation
9 = Stellar calibration
10 = Unreliable background subtracted
17 = unspecified error condition.

PT12S

0

127

127

Limb Retrieval Quality Flag

ICON_L24_Limb_Retrieval_Flags

Limb retrieval quality flag, where 0 = no limb inversion, 1 = retrieval nominal, 2 = number of iterations in retrieval algorithm reaches 10 without convergence, 3 = one or more inversion model parameters hits a priori upper or lower limit, 4 = altitude of peak intensity too close to boundary, 5 = standard deviation of one or more variables exceeds expected limit, 6 = Chi-squared value is outside of expected range - either too large or too small, 7 = one or more uncertainties is outside of expected range.

PT12S

0

10

-999

Local Solar Time of the Retrieval

ICON_L24_Local_Solar_Time

Local solar time of the retrieval, defined at 150 km tangent altitude, in WGS.

PT12S

hours

0

24

-999

Longitude of the Retrieval

ICON_L24_Longitude

Longitude of the retrieval, defined at 150 km tangent altitude, in WGS.

PT12S

degrees

0

360

-999

Model Error Flag

ICON_L24_Model_Flags

Diagnostic flag = 0 - nominal, flag(0)= 1 - 20 steps reached without converging, flag(1)=1 model para hit upper or lower limit, flag(2)=1 peak alt is too close to boundary.

PT12S

0

45

-999

Retrieved Altitude Profile of Nitrogen Molecules

ICON_L24_N2

Retrieved altitude profile of N2 from the retrieval, in cm-3, as a function of altitude and time.

PT12S

cm-3

0

100000002004087734272

-999

Retrieved Altitude Profile of Oxygen

ICON_L24_O

Retrieved altitude profile of oxygen from the retrieval, in cm-3, as a function of altitude and time.

PT12S

cm-3

0

100000002004087734272

-999

Retrieved Altitude Profile of Oxygen Molecules

ICON_L24_O2

Retrieved altitude profile of O2 from the retrieval, in cm-3, as a function of altitude and time.

PT12S

cm-3

0

100000002004087734272

-999

Geodetic Altitude (WGS84) of the Spacecraft

ICON_L24_Observatory_Altitude

Geodetic altitude (WGS84) of the spacecraft at the time corresponding to the middle of each FUV image, in kilometers.

PT12S

km

-600

600

-999

ICON Spacecraft WGS84 Latitude

ICON_L24_Observatory_Latitude

Geodetic latitude (WGS84) of the spacecraft at the time corresponding to the middle of each FUV image, in degrees.

PT12S

degrees

-90

90

-999

ICON Spacecraft WGS84 Longitude

ICON_L24_Observatory_Longitude

Geodetic longitude (WGS84) of the spacecraft at the time corresponding to the middle of each FUV image, in degrees.

PT12S

degrees

0

360

-999

Predicted Initial Column O/N2

ICON_L24_Predicted_Column_O_N2

Diagnostic Initial column O/N2 used by the limb retrieval, as a function of time.

PT12S

Dimensionless

0

45

-999

Initial Predicted Altitude Profile of Nitrogen Molecules

ICON_L24_Predicted_N2

Diagnostic Initial altitude profile of N2 used by the retrieval, in cm-3, as a function of altitude and time.

PT12S

cm-3

0

100000002004087734272

-999

Initial Predicted Altitude Profile of Oxygen

ICON_L24_Predicted_O

Diagnostic Initial altitude profile of O used by the retrieval, in cm-3, as a function of altitude and time.

PT12S

cm-3

0

100000002004087734272

-999

Initial Predicted Altitude Profile of Oxygen Molecules

ICON_L24_Predicted_O2

Diagnostic Initial altitude profile of O2 used by the retrieval, in cm-3, as a function of altitude and time.

PT12S

cm-3

0

100000002004087734272

-999

Predicted Ion Temperature

ICON_L24_Predicted_Temperature

Diagnostic Initial altitude profile of temperature used by the retrieval, in K, as a function of altitude and time.

PT1S

K

0

Inf

NaN

Retrieved Qeuv on the Disk

ICON_L24_QEUV

Diagnostic Effective solar EUV energy flux, mW/m2.

PT12S

mW/m2

0

100000002004087734272

-999

Standard Deviation of the Retrieved Nitrogen Molecules

ICON_L24_Sigma_N2

1 standard deviation of the retrieved N2 from the retrieval, as a function of altitude and time. The data product uncertainties are based on the measurement counting statistics and are lower limits because systematic uncertainties, which are expected to be much larger, are not included. The data processing complexity requires a qualitatively new uncertainty approach that must be derived from first principles.

PT12S

cm-3

0

100000002004087734272

-999

Standard Deviation of the Retrieved Oxygen

ICON_L24_Sigma_O

1 standard deviation of the retrieved O from the retrieval, as a function of altitude and time. The data product uncertainties are based on the measurement counting statistics and are lower limits because systematic uncertainties, which are expected to be much larger, are not included. The data processing complexity requires a qualitatively new uncertainty approach that must be derived from first principles.

PT12S

cm-3

0

100000002004087734272

-999

Standard Deviation of the Retrieved Oxygen Molecules

ICON_L24_Sigma_O2

1 standard deviation of the retrieved O2 from the retrieval, as a function of altitude and time. The data product uncertainties are based on the measurement counting statistics and are lower limits because systematic uncertainties, which are expected to be much larger, are not included. The data processing complexity requires a qualitatively new uncertainty approach that must be derived from first principles.

PT12S

cm-3

0

100000002004087734272

-999

Standard Deviation of the Column O/N2

ICON_L24_Sigma_O_N2'

1 standard deviation of the retrieved O/N2 from the retrieval, as a function of time. The data product uncertainties are based on the measurement counting statistics and are lower limits because systematic uncertainties, which are expected to be much larger, are not included. The data processing complexity requires a qualitatively new uncertainty approach that must be derived from first principles.

PT12S

Dimensionless

0

100000002004087734272

-999

Standard Deviation of the Ion Temperature

ICON_L24_Sigma_Temperature

1 standard deviation of the retrieved temperature from the retrieval, as a function of altitude and time. The data product uncertainties are based on the measurement counting statistics and are lower limits because systematic uncertainties, which are expected to be much larger, are not included. The data processing complexity requires a qualitatively new uncertainty approach that must be derived from first principles.

PT1S

K

0

Inf

-999

Solar Zenith Angle of the Retrieval

ICON_L24_Solar_Zenith_Angle

Solar zenith angle of the retrieval, defined at 150 km tangent altitude, in WGS.

PT12S

degrees

0

80

-999

Retrieved Altitude Profile of Temperature

ICON_L24_Temperature

Retrieved altitude profile of temperature from the retrieval, in K, as a function of altitude and time.

PT1S

K

0

100000002004087734272

-999

UTC Time String

ICON_L24_UTC_Time

UTC time corresponding to the retrieved parameters, in string format, as a function of time, in the format: 2017-05-27/00:00:01.435.

PT12S

Bad

Whole Day Retrieval Flags

ICON_L24_Whole_Day_Retrieval_Flag

Single flag set for whole day, where 0 = nominal data set, 1 = whole day skipped because no solar zenith angles were within range.

PT12S

integer

0

1

-999