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Data Access
FTPS from SPDF (not with most browsers)
HTTP access to files at SPDF
Subset, plot, list from CDAWeb
Fairbanks, Alaska
Falkland Is., United Kingdom
Lima, Peru
Quito, Equador
Santiago, Chile
Winkfield, United Kingdom
Alouette-2 Topside Sounder Ionogram Data
var authors='Whitteker, James H.';
document.write(authors);
(2025).
Alouette-2 Topside Sounder Ionogram Data.
[Data set].
Space Physics Data Facility.
https://doi.org/10.48322/fxfx-v946. Accessed on document.write(currentDateStr);.
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ResourceID
spase://NASA/NumericalData/Alouette2/SFS/PT31S
Description
These ionograms were digitized from the original Alouette 2 7-track analog telemetry tapes using the facilities of the former Data Evaluation Laboratory at the NASA/GSFC. This data restoration project is headed by Dr. R.F. Benson (NASA/GSFC). Ionograms were digitized at the rate of 40,000 16-bit samples/sec. This sample rate is higher than the Nyquist frequency of 30 kHz. The sample frequency of 40 kHz provides a measurement every 25 microseconds corresponding to an apparent range (c*t/2) interval of 3.75 km. The ionograms consist of swept-frequency operation (there is no fixed-frequency operation as in ISIS-1 and ISIS-2). The time resolution between ionograms is typically 31 seconds.
Metadata Rights
CC0-1.0:
Creative Commons Zero v1.0 Universal
Note
CC0 1.0 Universal is the Creative Commons license applicable to all publicly available SPASE metadata descriptions. The actual data/software may be subject to a different license.
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Version:2.7.1
NumericalData
ResourceID
spase://NASA/NumericalData/Alouette2/SFS/PT31S
NamingAuthority
NASA
ResourceType
NumericalData
ResourceHeader
ResourceName
Alouette-2 Topside Sounder Ionogram Data
DOI
https://doi.org/10.48322/fxfx-v946
ReleaseDate
2025-12-04 13:28:27Z
RevisionHistory
RevisionEvent
ReleaseDate
2021-04-04 21:14:17Z
Note
Only known prior ReleaseDate of the metadata
RevisionEvent
ReleaseDate
2025-11-14 16:01:55Z
Note
Added PublicationInfo. Added ResourceType and NamingAuthority. Changed http to https in top-level schemaLocation attribute. Fixed version number separator in top-level schemaLocation attribute. Matched version number in schemaLocation attribute to updated value in Version tag. ZCB
RevisionEvent
ReleaseDate
2025-12-04 13:28:27Z
Note
Added MetadataRightsList and RightsList(s). Updated to 2.7.1. ZCB
Description
These ionograms were digitized from the original Alouette 2 7-track analog telemetry tapes using the facilities of the former Data Evaluation Laboratory at the NASA/GSFC. This data restoration project is headed by Dr. R.F. Benson (NASA/GSFC). Ionograms were digitized at the rate of 40,000 16-bit samples/sec. This sample rate is higher than the Nyquist frequency of 30 kHz. The sample frequency of 40 kHz provides a measurement every 25 microseconds corresponding to an apparent range (c*t/2) interval of 3.75 km. The ionograms consist of swept-frequency operation (there is no fixed-frequency operation as in ISIS-1 and ISIS-2). The time resolution between ionograms is typically 31 seconds.
Acknowledgement
Users please acknowledge the Coordinated Data Analysis Web (CDAWeb) at the NASA Goddard Space Flight Center, Alouette-2 SFS instrument Principal Investigator J. H. Whitteker and Alouette/ISIS Data-Restoration project lead Robert F. Benson.
PublicationInfo
Authors
Whitteker, James H.
PublicationDate
2025-11-14 16:01:55Z
PublishedBy
Space Physics Data Facility
Contacts
Role
Person
StartDate
StopDate
Note
1.
PrincipalInvestigator
spase://SMWG/Person/James.H.Whitteker
2.
GeneralContact
spase://SMWG/Person/Robert.F.Benson
3.
GeneralContact
spase://SMWG/Person/Dieter.K.Bilitza
InformationURL
Name
ISIS/Alouette Topside Sounder Data Restoration Project
URL
https://spdf.gsfc.nasa.gov/isis/isis-status.html
Description
ISIS/Alouette page maintained by NASA GSFC with science and instrument descriptions, data access, software, and publication lists
Language
en
InformationURL
Name
NSSDC's Master Catalog
URL
https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1965-098A-01
Description
Information about the Sweep Frequency Sounder experiment on Alouette-2.
PriorIDs
spase://VWO/NumericalData/Alouette2/SFS/PT31S
spase://VSPO/NumericalData/Alouette2/SFS/PT31S
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF
Availability
Online
AccessRights
Open
RightsList
Rights
SchemeURI
https://spdx.org/licenses/
RightsIdentifierScheme
SPDX
RightsIdentifier
CC0-1.0
RightsURI
https://spdx.org/licenses/CC0-1.0.html
RightsName
Creative Commons Zero v1.0 Universal
Note
CC0 1.0 Universal is the Creative Commons license applicable to all publicly available NASA Heliophysics data products
AccessURL
Name
FTPS from SPDF (not with most browsers)
URL
ftps://spdf.gsfc.nasa.gov/pub/data/alouette/topside_sounder/ionogram_cdaweb/alouette2/
Description
FTP access to repository of Alouette-2 Ionograms in CDF format at NASA CDAWeb. The CDF files are organized by ground station, where each ground station is represented by a three letter ID and a two-digit code. The full names for each station are provided at https://spdf.gsfc.nasa.gov/isis/isis-table1-new.html
Language
en
AccessURL
Name
HTTP access to files at SPDF
URL
https://spdf.gsfc.nasa.gov/pub/data/alouette/topside_sounder/ionogram_cdaweb/alouette2/
Description
FTP access to repository of Alouette-2 Ionograms in CDF format at NASA CDAWeb. The CDF files are organized by ground station, where each ground station is represented by a three letter ID and a two-digit code. The full names for each station are provided at https://spdf.gsfc.nasa.gov/isis/isis-table1-new.html
Language
en
AccessURL
Name
Subset, plot, list from CDAWeb
URL
https://cdaweb.gsfc.nasa.gov/sp_phys/
Description
CDAWeb interactive interface for subsets, plots and lists of data
AccessURL
Name
Fairbanks, Alaska
URL
https://hpde.io/NASA/NumericalData/Alouette2/SFS/AverageIonogram/Fairbanks/PT31S
Description
Alouette-2 Topside Sounder Ionogram over Fairbanks, AK (SFS) (Latitude 65, Longitude 212)
AccessURL
Name
Falkland Is., United Kingdom
URL
https://hpde.io/NASA/NumericalData/Alouette2/SFS/AverageIonogram/FalklandIslands/PT31S
Description
Alouette-2 Topside Sounder Ionogram over Falkland Island, United Kingdom (SFS) (Latitude -52, Longitude 302)
AccessURL
Name
Lima, Peru
URL
https://hpde.io/NASA/NumericalData/Alouette2/SFS/AverageIonogram/Lima/PT31S
Description
Alouette-2 Topside Sounder Ionogram over Lima, Peru (SFS) (Latitude -12, Longitude 283)
AccessURL
Name
Quito, Equador
URL
https://hpde.io/NASA/NumericalData/Alouette2/SFS/AverageIonogram/Quito/PT31S
Description
Alouette-2 Topside Sounder Ionogram over Quito, Equador (SFS) (Latitude -1, Longitude 281)
AccessURL
Name
Santiago, Chile
URL
https://hpde.io/NASA/NumericalData/Alouette2/SFS/AverageIonogram/Santiago/PT31S
Description
Alouette-2 Topside Sounder Ionogram over Santiago, Chile (SFS) (Latitude -33, Longitude 298)
AccessURL
Name
Winkfield, United Kingdom
URL
https://hpde.io/NASA/NumericalData/Alouette2/SFS/AverageIonogram/Winkfield/PT31S
Description
Alouette-2 Topside Sounder Ionogram over Winkfield, United Kingdom (SFS) (Latitude 51, Longitude 359)
Format
CDF
Encoding
None
Acknowledgement
Users please acknowledge the Coordinated Data Analysis Web (CDAWeb) at the NASA Goddard Space Flight Center, ISIS-1 SFS instrument Principal Investigator J. H. Whitteker and ISIS Data-Restoration project lead Robert F. Benson.
ProcessingLevel
Calibrated
InstrumentIDs
spase://SMWG/Instrument/Alouette2/SFS
MeasurementType
Waves.Active
MeasurementType
Spectrum
TemporalDescription
TimeSpan
StartDate
1965-11-29 13:42:37Z
StopDate
1968-01-01 04:11:45Z
Note
The cadence is 31 s between ionograms. The Alouette-2 ionograms have the slowest sweep rate of any of the Alouette/ISIS topside sounders sweeping from 0.12 to 14.5 MHz in about 28 s with a frequency sweep rate of 0.13 MHz/s below 2.0 MHz (providing the highest frequency resolution of any of the sounders) and 1 MHz/s above 2 MHz. (Alouette 2 did not have a fixed-frequency operation).
Cadence
PT31S
SpectralRange
RadioFrequency
ObservedRegion
Earth.Magnetosphere
ObservedRegion
Earth.Magnetosphere.Polar
ObservedRegion
Earth.NearSurface.AuroralRegion
ObservedRegion
Earth.NearSurface.PolarCap
ObservedRegion
Earth.NearSurface.Ionosphere
ObservedRegion
Earth.NearSurface.Ionosphere.Topside
Keywords
Ionogram
topside sounder
swept-frequency sounder
topside ionosphere
ionospheric reflections
ground reflections
ionospheric echoes
ground echoes
ducted echoes
wave scattering
field-aligned irregularities
FAI
plasma resonance
plasma waves
AKR
solar type III bursts
upper-hybrid noise band
Parameter #1
Name
satellite ID
ParameterKey
satellite
Description
sat.-ID: 1=AL1, 2=AL2, 3=ISIS1, 4=ISIS2
Support
SupportQuantity
Other
Parameter #2
Name
telemetry station code
ParameterKey
station_id
Description
two-digit telemetry station code
Support
SupportQuantity
Other
Parameter #3
Name
transmitter power code
ParameterKey
power_code
Description
trans. power code: 1=Prim(400W) 2=Sec(400W)
Support
SupportQuantity
Other
Parameter #4
Name
sounder/receiver code
ParameterKey
s/r_code
Description
sounder/receiver code: 0=off, 1=on
Support
SupportQuantity
Other
Parameter #5
Name
pulse per second code
ParameterKey
pps_code
Description
pulse per second code: 0= 30 pps, 1= 60 pps
Support
SupportQuantity
Other
Parameter #6
Name
DMODE code
ParameterKey
DMODE
Description
DMODE (transm. on/off for alternate frame pairs): 0=off, 1=on
Support
SupportQuantity
Other
Parameter #7
Name
GMODE code
ParameterKey
GMODE
Description
GMODE (transmission of alternate frames of swept and fixed-frequency): 0=off, 1=on
Support
SupportQuantity
Other
Parameter #8
Name
sounder mixed mode
ParameterKey
mixed_mode
Description
sounder mixed mode (transmission at a fixed-frequency while the sounder receiver sweeps over swept-frequency range): 0=off, 1=on
Support
SupportQuantity
Other
Parameter #9
Name
fixed frequency code (0-6)
ParameterKey
fix_freq
Description
fixed frequency code: 0=off, 1=0.25, 2=0.48, 3=1.00, 4=1.95, 5=4.00, 6=9.303 MHz
Support
SupportQuantity
Other
Parameter #10
Name
Year
ParameterKey
year
Description
Year of ionogram frame sync in UT
Support
SupportQuantity
Other
Parameter #11
Name
Day of Year
ParameterKey
doy
Description
Day of Year of ionogram frame sync in UT
Support
SupportQuantity
Other
Parameter #12
Name
Hour
ParameterKey
hr
Description
Hour of ionogram frame sync in UT
Support
SupportQuantity
Other
Parameter #13
Name
Minute
ParameterKey
min
Description
Minute of hour of ionogram frame sync in UT
Support
SupportQuantity
Other
Parameter #14
Name
Second
ParameterKey
sec
Description
Second of minute of ionogram frame sync in UT
Support
SupportQuantity
Other
Parameter #15
Name
Local Mean Time (hh,mm)
ParameterKey
LMT
Description
Local Mean Time (hh,mm) at time of ionogram frame sync
Structure
Size
2
Element
Name
LMT(hh)
Index
1
Units
hrs
Element
Name
LMT(mm)
Index
2
Units
min
Support
SupportQuantity
Other
Parameter #16
Name
geog coord (Lat,Long,Hgt)
ParameterKey
geo_coord
Description
geographic coordinates (Lat,Long,Hgt) at time of ionogram frame sync
Structure
Size
2
Element
Name
latitude
Index
1
Units
deg
Element
Name
longitude
Index
2
Units
deg
Element
Name
height
Index
3
Units
km
Support
SupportQuantity
Positional
Parameter #17
Name
Geomagnetic Local Time (hh,mm)
ParameterKey
GMLMT
Description
Geomagnetic Local Time (HHMM) at time of ionogram frame sync
Structure
Size
2
Element
Name
GMLMT(hh)
Index
1
Element
Name
GMLMT(mm)
Index
2
Support
SupportQuantity
Other
Parameter #18
Name
geom latitude
ParameterKey
GMLAT
Description
geomagnetic latitude at time of ionogram frame sync
Units
deg
Support
SupportQuantity
Positional
Parameter #19
Name
geom longitude
ParameterKey
GMLONG
Description
geomagnetic longitude at time of ionogram frame sync
Units
deg
Support
SupportQuantity
Positional
Parameter #20
Name
Local Gyrofrequency
ParameterKey
FH
Description
Local Gyrofrequency at time of ionogram frame sync
Units
rad/s
Support
SupportQuantity
Other
Parameter #21
Name
inv latitude
ParameterKey
INV_LAT
Description
invariant latitude at time of ionogram frame sync
Units
deg
Support
SupportQuantity
Other
Parameter #22
Name
magnetic inclination
ParameterKey
DIP
Description
Dip angle of mag field direction at time of ionogram frame sync
Units
deg
Support
SupportQuantity
Other
Parameter #23
Name
Solar Zenith Angle
ParameterKey
CHI
Description
Solar Zenith Angle at time of ionogram frame sync
Units
deg
Support
SupportQuantity
Other
Parameter #24
Name
L shell (McIlwain parameter)
ParameterKey
L
Description
L shell (McIlwain parameter) at time of ionogram frame sync
Support
SupportQuantity
Positional
Parameter #25
Name
spacecraft in/out sunlight
ParameterKey
sun
Description
spacecraft in(=1)/out(=2) sunlight at time of ionogram frame sync
Support
SupportQuantity
Other
Parameter #26
Name
Cyl. Electrost. Probe
ParameterKey
CEP
Description
CEP instrument on(1)/off(0) status
Support
SupportQuantity
Other
Parameter #27
Name
0.05-30 kHz VLF receiver
ParameterKey
VLF
Description
VLF receiver on(1)/off(0) status
Support
SupportQuantity
Other
Parameter #28
Name
Spherical Electrostatic Analyzer
ParameterKey
SEA
Description
SEA instrument on(1)/off(0) status
Support
SupportQuantity
Other
Parameter #29
Name
Ion Mass Spectrometer 1
ParameterKey
IMS1
Description
IMS1 instrument on(1)/off(0) status
Support
SupportQuantity
Other
Parameter #30
Name
Ion Mass Spectrometer 2
ParameterKey
IMS2
Description
IMS2 instrument on(1)/off(0) status
Support
SupportQuantity
Other
Parameter #31
Name
Soft Particle Spectrometer
ParameterKey
SPS
Description
SPS instrument on(1)/off(0) status
Support
SupportQuantity
Other
Parameter #32
Name
Energetic Particle Detector
ParameterKey
EPD
Description
EPD instrument on(1)/off(0) status
Support
SupportQuantity
Other
Parameter #33
Name
start of swept-frequency portion
ParameterKey
swept_start
Description
scan line number of start of swept-frequency portion of the ionogram - seperates the fixed- and swept-frequency portions
Support
SupportQuantity
Other
Parameter #34
Name
times of ionogram frequency markers
ParameterKey
Time_mark
Description
msec after frame sync - time of frequency markers
Units
ms
Structure
Size
22
ValidMin
3000.0
ValidMax
30000.0
Support
SupportQuantity
Temporal
Parameter #35
Name
values of ionogram frequency markers
ParameterKey
freq_mark
Description
ionogram frequency markers
Units
MHz
Structure
Size
22
ValidMin
0.1
ValidMax
25.0
Support
SupportQuantity
Other
Parameter #36
Name
number of delay times per ionogram scan-line
ParameterKey
vh_num
Description
each sounder-pulse transmission is followed by a scan of the sounder-receiver video amplitude output values for each delay time monitored after the transmitted pulse; these scans are called scan lines. There are two types of ISIS-1 binary ionogram files, one designated as "full" and one as "average" The full file has 1340 delay times (one every 0.025ms). The average files are derived from the full files by averaging the amplitude values in 4 delay-time bins. Thus the average binary files contain 335 time-delay bins within each scan line. The cdf files were made from these average binary files.
Support
SupportQuantity
Other
Parameter #37
Name
number of ionogram scan-line frequencies
ParameterKey
f_num
Description
Ionogram files can be of different length. In some the swept-frequency portion covers the range 0.1 - 10 MHz, in others 0.1 - 20 MHz. Also, the proper start of each ionogram file, marked by a frame-sync pulse, was not always detected during the analog-to-digital (A/D) conversion. In such cases a frame sync was inserted to limit the file size. Thus the number of sounder-receiver video amplitude vs. delay time scan lines per ionogram can vary.
Support
SupportQuantity
Other
Parameter #38
Name
delay-time values
ParameterKey
delay_time
Description
delay-time values used in each scan line
Units
msec
Structure
Size
335
ValidMin
0.0
ValidMax
33.5
Support
SupportQuantity
Other
Parameter #39
Name
apparent-range values
ParameterKey
v_height
Description
apparent-range values used in each scan line
Units
km
Structure
Size
335
ValidMin
0.0
ValidMax
5025.0
Support
SupportQuantity
Other
Parameter #40
Name
Time
ParameterKey
Epoch
Description
Time
Units
ms
Support
SupportQuantity
Temporal
Parameter #41
Name
sounder receiver video amplitude
ParameterKey
ampl
Description
The sounder receiver linear video amplitude, from 0 to 255 telemetry units, in each apparent-range bin of each scan line covering the fixed- and swept-frequency regions. This range corresponds to a linear sounder-receiver video amplitude output range from zero to 4.5 V. This calibration is based on the video calibration pulse (of 3.0 V or 170 telemetry units) at the end of the line scan following each sounder pulse (the combined calibration pulses from all of the line scans produces a colored stripe at the bottom of the digital ionograms). In order to derive an input power level corresponding to the receiver video output it is necessary to know the sounder-receiver automatic-gain-control (AGC) voltage. This voltage was obtained from the pcm data and thus is only available if pcm data were available. The AGC voltage, which ranges from 0 to 5.12 volts, is obtained from a linear interpolation between the AGC trace displayed between 4005 km apparent range (26.7 ms delay time) as 5.12 V and 4395 km (29.3 ms delay time) as 0 volts. (On the full ionograms these numbers are 4001.250 km or 26.675 ms, and 4398.750 km or 29.325 ms.) On the average ionograms, which are available as either CDF or binary files from the SPDF or the NSSDC, the range resolution is 0.1 ms (corresponding to a virtual-range resolution of 15 km) there are 27 rows (26 intervals) covering the 0 to 5.12 V range; thus each row in virtual range above (decreasing delay time) the zero level (at 29.3 ms delay time) corresponds to an increase of 5.12/26 V of AGC with a quantization uncertainty of approximately plus or minus 0.1 V. Two rows have zero video-output amplitude values (on the average ionograms) in order that a clear AGC trace is visible on the ionograms. The row with the greatest virtual range corresponds to the actual AGC value. (On the full ionograms, which are only available as binary files from the NSSDC, the range resolution is 0.025 ms {corresponding to a virtual-range resolution of 3.75 km} and three rows have zero video-output amplitude values; the middle row corresponds to the actual AGC value.)
Structure
Size
335
ValidMin
0
ValidMax
255
Wave
WaveType
PlasmaWaves
Qualifier
Magnitude
Qualifier
Pseudo
WaveQuantity
Intensity
FrequencyRange
SpectralRange
RadioFrequency
Low
0.1
High
20
Units
MHz
Parameter #42
Name
scan-line frequency
ParameterKey
freq
Description
frequency of each scan line; in the swept-frequency portion of the ionogram they correspond to interpolated values between the frequency markers
Units
MHz
ValidMin
0.1
ValidMax
20.0
Support
SupportQuantity
Other