NOAA KLM User's Guide

Section 1.2.2

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1.2.2 Instrument Payload (General Descriptions) Earth Imaging

The AVHRR/3, a six-channel scanning radiometer, views the same Earth area with each channel. The data acquired during each scan allows, after ground processing, multispectral analysis of hydrologic, oceanographic, land use and meteorological parameters. Data from channels l, 2, and 3A are used to monitor reflected energy in the visible and near-IR portions of the electromagnetic spectrum. These data provide means to observe vegetation, clouds, lakes, shorelines, snow, aerosols and ice. Data from channels 3B, 4 and 5 are used to determine the radiative energy from the temperature of the land, water, and sea surface as well as the clouds above them. Only five channels can be transmitted simultaneously, channels 3A and 3B being respectively switched for day/night operation and as determined by operational requirements for the afternoon satellite, while 3B will be on continuously for the morning satellite mission. For the first time, Channels 1, 2 and 3A on these spacecraft have incorporated the low light split-gain provision, providing better resolution in a portion of the radiance range. The Automatic Picture Transmission (APT) mode, using two selected channels, produces a more geometrically linear scan line but at the reduced resolution of 4 km. Table lists the six channels and their required spectral, spatial and thermal resolution (where appropriate). For more information on the AVHRR/3 instrument, see Section 3.1.

Table AVHRR/3 Channels.
Channel Spectral Bandpass (micrometers) Spatial Resolution at nadir (km) Signal to Noise (S/N) or Noise Equivalent Delta Temperatures (NEΔT)
1 (Visible) 0.580 - 0.68 1.1 9:1 at 0.5% Albedo
2 (Near IR) 0.725 - 1.00 1.1 9:1 at 0.5% Albedo
3A (Near IR) 1.580 - 1.64 1.1 20:1 at 0.5% Albedo
3B (IR-Window) 3.550 - 3.93 1.1 0.12 K at 300 K
4 (IR-Window) 10.300 - 11.3 1.1 0.12 K at 300 K
5 (IR-Window) 11.500 - 12.5 1.1 0.12 K at 300 K Atmospheric Sounding Instruments

Three instruments are used to determine radiance needed to calculate the atmospheric temperature and humidity profiles form the earth's surface to the stratosphere. These instruments are the High-Resolution Infrared Sounder/3 (HIRS/3), the Advanced Microwave Sounding Unit-A (AMSU-A) and the Advanced Microwave Sounding Unit-B (AMSU-B) for NOAA KLM.

The HIRS/3 has twenty spectral bands, nineteen in the IR band and one in the visible band. This instrument is basically the same as the instrument flown on earlier spacecraft, except for five spectral band changes to improve sounding parameter accuracy. The instrument measures scene radiance in nineteen channels to permit calculation of the vertical temperature profile from the Earth's surface to about 40 km. The instrument scans ±49.5 degrees, having a ground resolution (nadir) of 17.4 km, 56 instantaneous fields of view (IFOV) for each 2250-km scan line at 6.4 seconds per scan line and 42 km between IFOV's along-track (nadir). See Section 3.2 for the required wavelength, half-power bandwidth and noise power requirements for the HIRS/3.

The AMSU-A is a total power radiometer and a line scan instrument designed to permit the calculation of the vertical temperature profile from the Earth's surface to about a 2-millibar pressure height 45 km (28.0 mi). Vertical profiles are obtained through the measurements of scene radiance in fifteen channels, ranging from 23.8 to 89 GHz. The instrument has an instantaneous field-of-view of 3.3 degrees at the half-power points. The antenna provides a cross-track scan, scanning ±50 degrees from nadir with a total of 30 Earth fields of view per scan line. Each Earth field of view is separated from the adjacent cell along the scan direction by 3 1/3 degrees. Spatial resolution at nadir is nominally 50 km (31.0 mi). See Section 3.3 for more details on AMSU-A.

The AMSU-B is a line scan instrument designed to allow the calculation of the vertical water vapor profiles from the Earth's surface to about a 20-millibar pressure 12 km (7.5 mi). Vertical profiles are obtained through the measurements of scene radiance in five channels, ranging from 89 to 183 GHz. AMSU-B, like the AMSU-A, is a total power radiometer and uses two target temperatures to provide for accurate radiance calibration with each scan. The instrument has an instantaneous field-of-view of 1.1 degrees at the half-power points. The antenna provides a cross-track scan, scanning of ±49.5 degrees from nadir with a total of 90 Earth fields of view per scan line. Each Earth field of view is separated from the adjacent cell along the scan direction by 1.1 degrees. Spatial resolution at nadir is nominally 16.7 km (10.4 mi). AMSU-B contains four water vapor channels (channels 17 through 20 inclusive) and one window channel (channel 16). AMSU-A channel 15 and AMSU-B channel 16 share the same atmospheric window band. See Section 3.4 for more details on AMSU-B. Solar Backscatter Ultraviolet Radiometer (SBUV)

The SBUV/2 is a non-spatially scanning, spectrally scanning sounding radiometer. It is designed to measure scene radiance and solar spectral irradiance in the spectral range from 160 to 406 nanometers (nm). In the discrete mode, measurements are made in 12 spectral bands from which the total ozone and vertical distribution of the ozone are deduced. The sweep mode provides a continuous spectral scan from 406 to 160 nm that is used primarily for solar spectral irradiance measurements. The half power FOV is 11.33 degrees or 172 km (106.9 mi). Spectral characteristics are described in Table

Table SBUV/2 Spectral Characteristics (Discrete Mode).
Step Number Central Wavelength (nm) Bandwidth (nm)
1 252.00 ±0.05 1 + 0.2, -0
2 273.61 ±0.05 1 + 0.2, -0
3 283.10 ±0.05 1 + 0.2, -0
4 287.70 ±0.05 1 + 0.2, -0
5 292.29 ±0.05 1 + 0.2, -0
6 297.59 ±0.05 1 + 0.2, -0
7 301.97 ±0.05 1 + 0.2, -0
8 305.87 ±0.05 1 + 0.2, -0
9 312.57 ±0.05 1 + 0.2, -0
10 317.56 ±0.05 1 + 0.2, -0
11 331.26 ±0.05 1 + 0.2, -0
12 339.89 ±0.05 1 + 0.2, -0
Cloud Cover Radiometrics 379.00 ±1 3 + 0.3 Space Environment Monitor (SEM)

The SEM-2 provides measurements to determine the intensity of the Earth's radiation belts and data on charged particle precipitation phenomena in the upper atmosphere resulting from solar activity. It provides warnings of solar occurrences that may impair long-range radio communication or high-altitude manned operations.

The SEM-2 consists of two separate sensor units and a common Data Processing Unit (DPU). The sensor units are the Total Energy Detector (TED) and the Medium Energy Proton and Electron Detector (MEPED). Performance characteristics are given in Table

Table SEM-2 Characteristics.
SEM-2 Units Performance Requirements Energy Levels Field of View
TED Determine heat energy input into upper atmosphere from absorption of electrons, protons and positive ions. Electrons: 0.05 keV to 20 keV

Protons: 0.05 keV to 20 keV

Two at 15 degrees full angle,

-x, -x + 30 degrees

MEPED Same as TED Electrons: 30 keV to 7000 keV

Protons: 30 keV to 6900 keV

Above >16, >35, >70, >140 MeV

15 degrees full angle
-x, -x +90 degrees

15 degrees full angle
-x, -x +90 degrees

120 degrees full angle, -x

DPU Combine outputs into a 2-second, 40-word format. Provide command, calibrate and timing interfaces.
System Summary (Maximums) Mass: 15 kg
Power: 10 Watts
Volume: 0.0186 m3
Telemetry: Two (8-bit) words/TIP minor frame

The TED uses eight programmed swept electrostatic curved-plate analyzers to select particle type and energy and Channeltron detectors to sense and quantify the intensity in the sequentially selected energy bands. The particles of interest have energies ranging from 50 electron volts (eV) to 20 keV.

The MEPED senses protons, electrons and ions with energies from 30 keV to several tens of MeV. The MEPED is a collection of four directional solid-state detector telescopes and four "generally omnidirectional" sensors.

Accumulators are located in the DPU to sort and count the events. The processed data are multiplexed and fed to the satellite telemetry system.

The SEM-2 data are separated from the other data by NOAA/NESDIS and, along with orbital element data, are sent to the Space Environment Center (SEC) in Boulder, Colorado for processing. Search and Rescue Satellite Aided Tracking System

The SARSAT system is designed to detect and locate Emergency Locator Transmitters (ELTs) and Emergency Position-Indicating Radio Beacons (EPIRBs) operating at 121.5, 243, and 406.05 MHz. Figure illustrates the SARSAT concept.

Figure showing SARSAT concept

The SAR instrumentation on the NOAA KLM satellites comprise two elements, the SARR and the SARP-2. Table summarizes the SARSAT instrumentation characteristics.

Table SARSAT Subsystem Characteristics.
Spacecraft Repeater (121.5, 243, and 406 MHz):
Parameter Specification
Bandwidths (Doppler shift + drift + Tolerance + guardband):
121.5 MHz 25 kHz
243 MHz 46 kHz
406.050 MHz 100 kHz
Transmitter Power (1,544 MHz) 8 W decibels referenced to a watt (dBW)
Physical Characteristics:
Weight 24 kg
Size 0.034 m3
Power 53 W
Spacecraft 406 MHz Processor:
Maximum Bandwidth 80 kHz
Storage Capacity 324 kb
Output Data Rate (via Telemetry) 2.4 kbps
Physical Characteristics:
Weight 27.5 kg
Size 0.034 m3
Power 33 W Data Collection System

The DCS/2 collects global telemetry data using a one-way radio frequency (RF) link 401.65 Mhz from data collection platforms in the form of buoys, free-floating balloons, and remote weather stations and processes these inputs for on-board storage and subsequent transmission from the satellite. For free-floating telemetry transmitters, the system determines the location within 5 km to 8 km root mean square (rms) and velocity to an accuracy of 1 meter per second (mps) to 1.6 mps rms. Other characteristics are shown in Table Measurements of environmental data are telemetered to the satellite for collection. The DCS/2 supplements the GOES data collection system in collecting both the information from the more-northern and more-southern latitudes and the location data on free-floating transmitters.

Table DCS/2 System Characteristics.
Parameter Characteristic
Minimum satellite elevation angle from platform 5 degrees
Number of platforms requiring location/velocity measurements visible in a 5 degree visibility circle Capacity: 230
Total number of such platforms over the globe Capacity: 4100
Percentage of platforms with six good Doppler measurements per day 85%
Platform transmission repetition period Approx. 60 sec
Message length 0.3 to 0.9 sec
Expected location accuracy 5 km to 8 km rms
Expected velocity accuracy 1 to 1.6 mps

For the incoming signals, the DCS/2 measures frequency and relative time. The formatted data are stored in the satellite for transmission to the CDA station. The DCS/2 data are stripped from the GAC data by NOAA/NESDIS and transmitted to the ARGOS center at the Centre National d'Etudes Spatiales (CNES) in Toulouse, France, for processing, distribution to users and storage for archival purposes. Alternatively, there is an operational feature that allows the stored data to be acquired directly by a European ground station.

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