GOES
Introduction

The Geostationary Operational Environmental Satellite (GOES) series of satellites is owned and operated by the National Oceanic and Atmospheric Administration (NOAA). The National Aeronautics and Space Administration (NASA) manages the design, development and launch of the spacecraft. Once the satellite is launched and checked out, NOAA assumes responsibility for the command and control of the satellite, transmission of data, and the archive and dissemination of the data and its derived products to the user community.

The NOAA National Climatic Data Center (NCDC) is responsible for the long term archive of GOES data, while the NOAA National Environmental Satellite, Data, and Information Service (NESDIS) operates the satellites and is responsible for providing real-time data and products.

Where Polar-orbiting Operational Environmental Satellites (POES) provide daily global coverage for analyzing long-term climatic and environmental trends, the GOES satellites' primary goal is to monitor the atmosphere for severe weather development such as tornadoes, flash floods, hail storms and hurricanes. When these conditions develop, the GOES satellites can track storms on a minute to minute basis.

The GOES satellite is positioned 35,790 km (22,240 statute miles) above the equator allowing it to view a major portion of the Western Hemisphere including southern Canada, the contiguous 48 states, major portions of the eastern Pacific Ocean and western Atlantic Ocean and Central and South America. Because the Atlantic and Pacific basins strongly impact the weather over the United States, coverage is typically provided by two GOES spacecraft, one at -75.0 Longitude (GOES East) and the other at -135.0 Longitude (GOES West).

The combined footprint (radiometric coverage and communications range) of the two spacecraft encompasses Earth's full disk about the meridian approximately in the center of the continental United States.

GOES Image

Availability of GOES operational radiance data in CLASS is shown in the following table. 

Satellite Start Date End Date  Location

SMS-1

01/26/79

04/19/79

East

SMS-2+

04/19/79

08/05/81

East

GOES-1

11/29/82

05/31/83 

Variable

GOES-2

02/20/78

01/26/79

East

GOES-3

11/20/78

03/05/81

West

GOES-4

03/05/81

11/26/82

West

GOES-5

08/05/81

07/30/84

East

GOES-6

06/01/83

01/21/89

Variable

GOES-7

03/25/87

01/09/96

Variable

GOES-8

09/01/94

04/01/03

East

GOES-9

01/09/96

07/21/98

West

GOES-9++

04/23/03

07/13/04

GMS-5

GOES-10

07/21/98

06/21/06

West

GOES-11

06/21/06

12/06/11

West

GOES-12

04/01/03

04/14/10

East

GOES-13

04/14/10
10/18/12*

09/23/12
Present

East

GOES-14 09/23/12 10/18/12 East
GOES-15 08/02/11 Present West

Legend
+ SMS-2 operation was intermittent
++ GOES-9 replacement for GMS-5 over western Pacific - limited data in CLASS
Satellites were moved to different orbital positions to fulfill seasonal operational needs during times when there was a single satellite configuration.
* GOES-13 data gap from Sep 23, 2012 to Oct 18, 2012 due to an anomaly
^ GOES-14 was placed into service during GOES-13 outage.

The GOES information that follows is specific to the current series of satellites (i.e. from GOES-8 forward). For users needing technical information for the earlier satellites, please go to the Comprehensive Information section for links to technical documents and guides.

Application

The objective of the GOES satellites is to provide continuous, timely and high-quality environmental and atmospheric observations over much of the Western Hemisphere to enable forecasters to more accurately predict weather conditions and monitor and track severe storms. GOES data are used in a number of forecast situations such as estimating heavy rainfall, measuring movement and strengths of tropical storms, tracking volcanic plumes for aviation safety, measuring sea-surface temperatures, and much more. Since the GOES data archive extends well over two decades, its applications in long-term climate studies are being used by scientists around the world.

Data Acqusition

GOES Data Acquisition Introduction

The GOES Support System includes the Command and Data Acquisition (CDA) Station at Wallops Island, VA, and the NOAA Satellite Operations Facility (NSOF)at Suitland, MD. At the CDA station, raw instrument data and telemetry are read out from the satellite. Data are processed, calibrated, earth-located and converted to GOES VARiable data format (GVAR) and rebroadcast to the satellite along with spacecraft command schedules. The GVAR data are then broadcast to direct readout users. NSOF is responsible for the overall safety of the spacecraft, scheduling of the instruments, data quality and performance. Continuous monitoring and checks are conducted on orbital position, image navigation and registration, and various subsystems including primary imager and sounder instruments. It is also responsible for planning and operating the ground system equipment for GVAR acquisition at NESDIS, the initial stage of product processing. The Office of Satellite Data Processing and Distribution (OSDPD) manages and directs the operation of the central ground facilities which ingest, process, and distribute environmental satellite data and derived products to domestic and foreign users.

GOES System Functions and Instruments

The GOES spacecraft performs three major functions:

  • Environmental Sensing: Acquisition, processing and dissemination of imaging and sounding data, independent of imaging data processes and the (in-situ) space environment monitoring data, and measurement of the near-earth space weather�.
  • Data Collection: Receive data from earth surface-based Data Collection Platforms (DCPs) and relay to various acquisition stations.
  • Data Broadcast: Continuous relay of weather facsimile and other meteorological data to independent users, research and educational institutions; relay of distress signals from aircraft or marine vessels to the search and rescue ground station of the search and rescue satellite-aided tracking system.

Each mission function is supported or performed by components of the GOES payloads:

Environmental Sensing:

  • Five-channel Imager
  • Nineteen-channel Sounder
  • Space Environment Monitor (SEM)
    • Energetic Particles Sensor (EPS)
    • High energy proton and alpha particle detector (HEPAD)
    • X-ray Sensor (XRS)
    • Magnetometers

Data Collection:

Data Collection System (DCS)

Data Broadcast

  • Processed Data Relay (PDR) and Weather Facsimile (WEFAX) transponders
  • Search And Rescue (SAR)
  • Sensor data and Multiuse Data Link (MDL) transmitters

The remote sensing function is carried out by the 5-channel Imager and 19-channel Sounder. The acquisition of sensed data and its handling, processing, and final distribution are performed in real-time to meet observation time and timeliness requirements, including revisit cycles. Remotely sensed data are obtained over a wide range of areas of the western hemisphere, encompassing the earth's disk, selected sectors and small areas. Area coverage also includes the visibility needed to relay signals and data from ground transmitters and platforms to central stations and end users.

 

Imager

Imager Introduction

The Imager instrument is designed to sense radiant and solar-reflected energy from sampled areas of the Earth's surface and atmosphere. The Imager's five spectral channels simultaneously sweep an 8 km north-south (N/S) longitudinal swath along an east-west (E/W) latitudinal path by means of a two-axis gimballed mirror scan system. Beamsplitters separate the spectral channels into the various IR detector sets.

The primary characteristics of the imager are defined in the following tables:

Imager Instrument Characteristics:

Channel

Detector Type

Nominal Square IGFOV at nadir

1 (Visible)

Silicon

1 km

2 (Shortwave)

InSb

4 km

3 (Moisture)

HgCdTe

8 km (4 km GOES 12/13/14/15)

4 (Longwave 1)

HgCdTe

4 km

5 and 6 (Longwave 2)

HgCdTe

4 km



Imager Instrument Parameters:

Parameter

Performance

FOV defining element

Detector

Channel-to-channel alignment

28 µ rad (1.0 km) at nadir

Radiometric calibration

300 K internal blackbody and space view

Signal quantizing

10 bits, all channels

Scan capability

Full earth, sector, area

Output data rate

2,620,800 b/s

Imaging areas

20.8° E/W by 19° N/S



Imaging Channels Allocation:

Channel Number

Wavelength Range (µm)

Range of Measurement

1

0.55 to 0.75

1.6 to 100% albedo

2 (GOES 8/9/10)
2 (GOES 11/12)

3.80 to 4.00
3.80 to 4.00

4 to 320 K
4 to 335 K

3 (GOES 8/9/10/11)
3 (GOES 12/13/14/15)

6.50 to 7.00
5.77 to 7.33

4 to 320 K

4

10.20 to 11.20

4 to 320 K

5 (GOES 8/9/10/11)

11.50 to 12.50

4 to 320 K

6 (GOES 12/13/14/15)

12.96 to 13.72

4 to 320 K



Imager Performance Summary:

Parameter

Performance

System absolute accuracy

Infrared channel ≤ 1 K
Visible channel ± 5% of maximum scene radiance

System relative accuracy

Line to line ≤0.1 K
Detector to detector ≤0.2 K
Channel to channel ≤0.2 K
Blackbody calibration to calibration ≤0.35 K

Star sense area

21° N/S by 23° E/W

Imaging rate

Full earth ≤ 26 min

Time delay

≤3 min

Fixed Earth projection and grid duration

24 hours

Data timeliness
Spacecraft processing
Data coincidence

≤30 s
≤5 s

Imaging periods
Image navigation accuracy @
nadir
Registration within an image*
Registration between repeated images*


* For spec orbit




25 min
15 min
90 min
24 h
48 h

Noon ±8 hrs

4 km
50 µrad
53 µrad
84 µrad
168 µrad
210 µrad

Midnight  ±4 hrs

6 km
50 µrad
70 µrad
105 µrad
168 µrad
210 µrad

Channel-to-channel registration

 

28 µrad

50 µrad
(IR only)



Imager Scanning Characteristics

The Imager scans predetermined areas in alternate directions on alternate lines. The imaging area is defined by a coordinate system related to the instrument's orthogonal scan axis. During imaging operations a scan line is generated by rotating the scanning mirror in the east-west direction while concurrently sampling each of the active imaging detectors. At the end of the line, the Imager scan mirror performs a turnaround, which involves stepping the mirror to the next scan line and reversing the direction of the mirror. The next scan is then acquired by rotating the scanning mirror in the opposite, west-east direction, again with concurrent detector sampling. Detector sampling occurs within the context of a repeating data block format. In general, all visible detectors are sampled four times for each data block (four times 1 km wide); while each of the active IR detectors is sampled once per data block (one times 4 km wide).

There are three operational imaging modes which satisfy a number of requirements defined by the NOAA NESDIS/NWS Study Group. The operational modes are designated as Routine, Rapid Scan and Super Rapid Scan. The tables below provide information on coverage, scan duration and scan times for GOES-East and GOES-WEST during Routine operational mode.

GOES-EAST Imager Scan Sectors in Routine Mode

Frame Name

Boundaries

Duration
(mm:ss)

Scan Times
(UTC)

Full Earth

Earth Edge

26:16

0245, 0545, 0845, etc

Extended N Hemisphere

20S-66N/45-120W

14:16

xx15, xx45

Southern Hemisphere

20-50S/30-120W

4:53

xx10, xx40

CONUS

14-60N/60-125W

4:45

xx00, xx30



GOES-WEST Imager Scan Sectors in Routine Mode>

Frame Name

Boundaries

Duration
(mm:ss)

Scan Times
(UTC)

Full Earth

Earth Edge

26:10

0000, 0300, 0600, etc

Northern Hemisphere

0-66N/90W-170E

9:00

xx00, xx30

Southern Hemisphere

0-45S/115W-170E

7:00

xx22, xx52

PACUS

12-60N/90-175W

5:00

xx15, xx45



During GOES Rapid Scan Operations (RSO), four views of the continental United States (CONUS) are provided at approximately 7.5 minute intervals in a half hour period. A northern hemisphere scan for both GOES East and GOES West satellites is also included in the 30 minute cycle. This yields eight views of the continental U.S. per hour.

During GOES Super Rapid Scan Operations (SRSO), approximately 10 one-minute interval scans are provided every half hour using prescribed 1000 x 1000 km sectors. The remaining time in the half hour cycle is devoted to scans of the northern hemisphere and CONUS (or sub-CONUS for GOES-WEST).

When GOES RSO or SRSO is utilized, most of the southern hemisphere is not scanned.

Imager Data Characteristics

GOES data transmitted from the satellites and received by users with ground receiving equipment is called GVAR data. This format is primarily used to transmit meteorological data measured by the Imager and Sounder instruments and is archived in this format but rarely provided in this format to users of retrospective data due to its complex nature.

The GVAR format has its origins in the Operational VAS Mode AAA format, which featured a fixed length format composed of 12 equal size blocks of data. These blocks were transmitted synchronously with the spin of the earlier GOES (i.e. one complete 12 block sequence occurred for each rotation of the satellite.

With the launch of GOES-8 in April 1994, the spin-scan satellites were replaced by three-axis stabilized GOES. The continued use of the old transmission format would have been detrimental to the operational capabilities of these satellites. Therefore, the GVAR format was developed. GVAR maintained as much commonality with the Mode AAA reception equipment that many users had invested in and permitted full use of the advanced data transmission technology.

Imager Calibration

The raw data in the visible channel are relativized and normalized at the CDA, but no calibration is applied. The raw data in the IR channels are calibrated using spacelooks and a heated internal blackbody. The spacelook calibration positions the scanning mirror at an extreme E-W coordinate permitting a view of space. The frequency of these spacelooks depends on the activity of the instrument. The rates vary from once every second to once every 36.6 seconds. A Blackbody calibration sequence is initiated every 30 minutes. During the sequence, the scanning mirror is rotated in the N-S direction through an angle of approximately 180 degrees to present a view of the Blackbody surface to the imaging detectors. The Blackbody surface temperature is maintained at a nominal 290Ëš K. For more information on GOES calibration see http://www.oso.noaa.gov/goes/goes-calibration/index.htm.

Sounder

Sounder Introduction

The Sounder operates independently of the Imager and is designed to measure atmospheric temperature and moisture across large regions of the western hemisphere. The instrument contains 18 IR channels and one visible channel. There are four detectors for each band. Each detector's Field of View (FOV) is 8 km at nadir. The scan swath width is 40 km wide (N-S). The infrared spectral definition is provided by a rotating filter wheel that brings selected filters into the optical path of the detector assembly. Filters in three spectral ranges, longwave (12µm to 14.7µm), midwave (6.5µm to 11µm), and shortwave (3.7µm to 4.6µm), are arranged on the wheel for efficient use of sample time and optimal channel co-registration. The rotation of the filter wheel is synchronized with the stepping motion scan mirror. The visible channel (0.67µm) is not part of the filter wheel but is a separate set of uncooled silicon detectors having the same field of view size and spacing. These detectors are sampled at the same time as IR channels 3, 11, and 18, providing registration of all sounding data.

The primary characteristics of the sounder are defined in the following tables:

Sounder Instrument Characteristics:

Channels

Detector Type

Nominal Circular IGFOV (µrad)

1 to 7 (LW IR)

HgCdTe

242

8 to 12 (MW IR)

HgCdTe

242

13 to 18 (SW IR)

InSb

242

19 (visible)

Silicon

242

Star sense

Silicon

28*

*square detectors

Sounder Instrument Parameters:

Parameter

Performance

FOV defining element

Field stop

Telescope aperture

31.1-cm (12.2-in) diameter

Channel definition

Interference filters

Radiometric calibration

Space and 300 K IR blackbody

Field sampling

Four areas N/S on 280 µrad centers

Scan step angle

280 µrad (10-km nadir) EW

Step and dwell time

0.1, 0.2, 0.4s adjustable

Scan capability

Full earth and space

Sounding areas

10 km by 40 km to 60° N/S and 60° E/W

Signal quantizing

13 bits, all channels

Output data rate

40 kb/s

Channel-to-channel alignment

22 µrad



Sounder Detectors Channel Allocation:

Detector

Channel Number

Wavelength (Åm)

Wave No. (cm-1)

Longwave

1
2
3
4
5
6
7

14.71
14.37
14.06
13.64
13.37
12.66
12.02

680
696
711
733
748
790
832

Midwave

8
9
10
11
12

11.03
9.71
7.43
7.02
6.51

907
1030
1345
1425
1535

Shortwave

13
14
15
16
17
18

4.57
4.52
4.45
4.13
3.98
3.74

2188
2210
2248
2420
2513
2671

Visible

19

0.70

14367



Sounder Performance Summary:

Parameter

Performance

System absolute accuracy

Infrared channel ≤ 1 K
Visible channel ± 5% of maximum scene radiance

System relative accuracy

Line to line ≤25 K
Detector to detector ≤40 K
Channel to channel ≤29 K
Blackbody calibration to calibration ≤60 K

Star sense area

21° N/S by 23° E/W

Sounding rate

3000 by 3000 km ≤ 42 min

Time delay

≤3 min

Visible channel data quantization

≤1% albedo

Infrared channel data quantization

1/3 specified noise equivalent radiance difference (NE∆N)

Data timeliness
Spacecraft processing

≤ 30 s

Sounding periods
Image navigation accuracy
at nadir
Registration within 120 minute sounding
Registration between repeated soundings





120 min

24 h

Noon ±8 hrs

10 km

84µrad

280µrad

Midnight ±4 hrs

10 km

112µrad

280µrad

channel-to-channel registration

 

28µrad

28µrad



Sounder Scanning Characteristics

Like the Imager, the Sounder scans the selected image area in alternate directions on alternate lines. This area is defined by scan coordinates which relate to the latitude and longitude for the northwest corner and southeast corner. The Sounder, however, provides additional scanning features that are not employed on the Imager. This instrument provides the capability to dwell on a particular location for a pre-programmed time period. These dwell times are 0.1, 0.2, or 0.4 seconds for one, two, or four data blocks. The Sounder also employs two N/S scanning modes referred to as the single and double-step modes. When in the single-step mode, the scan mirror steps the equivalent of one output scan line in the N-S direction each time an E-W or W-E scan completes. In the double-step mode, the scan mirror steps two output scan lines in the N-S direction for each E-W or W-E scan. This mode is also referred to as the skip-line mode and will only scan an image area with a dwell of 0.1 second. The single-step mode of operation is considered the normal mode for the Sounder and can scan an image area at any of the three dwell selections.

The tables below show the sounder scan areas, their boundaries, duration and scan times. The scan durations do not include star looks or blackbody calibration operations.

GOES-EAST Sounder Scan Sectors in Routine Mode

Frame Name

Boundaries

Duration
(mm:ss)

Scan Times
(UTC)

Full Regional N. Hem.

23-53N/64-121W

49:00

xx05 (hourly)

Limited Regional N Hem

26-50N/66-120W

38:00

4x daily

Full Regional S. Hem.

27-41S/64-120W

49:00

4x daily (winter)

Mesoscale Tropics

11-23N/93-115W

12:00

4x daily (summer)



GOES-WEST Sounder Scan Sectors in Routine Mode

Frame Name

Boundaries

Duration
(mm:ss)

Scan Times
(UTC)

Regional (ASOS1)

22-50N/128-175W

32:00

xx24 (hourly)

Regional (ASOS2)

21-50N/109-125W

20:00

xx01 (hourly)

Limited (ASOS2)

31-50N/128-175W

20:00

4x daily

Hurricane Sector (Area1)

06-23N/102-137W

32:00

4x daily (summer)

Hurricane Sector (Area2)

06-23N/137-178W

32:00

4x daily (summer)



Sounder Data Characteristics

The raw Sounder data is also part of the GVAR transmission, which consists of twelve distinct blocks numbered 0 through 11. Blocks 0 through 10 are transmitted as a contiguous set for each Imager scan. Block 10 will be followed by a variable number of Block 11's, which are always at fixed lengths. All sounder data will be included in Block 11, but not all Block 11's will contain sounder data. As the GVAR data are received by NOAA, the sounder blocks are stripped out and converted into McIDAS AREA format for final archive.

 

Sounder Calibration

The Sounder performs a spacelook calibration sequence at a fixed nominal rate every 2 minutes. During a Sounder spacelook calibration, 40 raw Sounder data blocks are acquired at the spacelook coordinates. Unlike the Imager, the Sounder has no defined preclamp or clamp activity. A data analyses is also performed for the Sounder spacelook data. The resulting statistics are packaged in the Sounder Block 11. The Sounder performs a Blackbody sequence every 20 minutes. During the sequence, the scanning mirror is rotated in the N-S direction through an angle of approximately 180 degrees to present a view of the Blackbody surface to the imaging detectors. Like the Imager, the Blackbody surface temperature is maintained at a nominal 290˚ K.. For more information on GOES calibration see http://www.oso.noaa.gov/goes/goes-calibration/index.htm.

Comprehensive Information

Detailed technical information on the GOES spacecraft and instruments is found in two publications:
GOES I-M DataBook for GOES-8 through GOES-12 and GOES N Series DataBook for GOES-13/14/15. These copies are availabe in PDF format and can be donwloaded in its entirety or in sections at:
http://goes.gsfc.nasa.gov/text/goes.databook.html (GOES-8 to 12)
http://goes.gsfc.nasa.gov/text/goes.databooknop.html (GOES-13 to 15)

A full description of the GVAR transmission format is located at http://www.osd.noaa.gov/gvar/gvardownload.htm.

Additional information on GOES operations can be found at the NOAA Satellite Information Services web site at http://noaasis.noaa.gov/NOAASIS/ml/gateway.html

GOES Products & Services Catalog: http://www.orbit.nesdis.noaa.gov/smcd/opdb/goescat_v4/.

The GOES Data Users Guide can be found at http://www1.ncdc.noaa.gov/pub/data/documentlibrary/tddoc/td3701.pdf.

For details on the GOES Mode formats, please click on the appropriate links below (caution: intended for GOES data experts)

http://www.ncdc.noaa.gov/oa/documentlibrary.Mode_A.pdf
http://www.ncdc.noaa.gov/oa/documentlibrary/Mode_A_Update_100182.pdf
http://www.ncdc.noaa.gov/oa/documentlibrary/Mode_AA_RevB.pdf
http://www.ncdc.noaa.gov/oa/documentlibrary/Mode_AA_RevC.pdf
http://www.ncdc.noaa.gov/oa/documentlibrary/Mode_AAA.pdf

For helpful information to read, calibrate, or navigate GOES data please click on the link below.

http://www.ncdc.noaa.gov/oa/rsad/satfaq/satfaq.html

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