2017-02-21

HF Beacons

One of the purposes of the RBN is to allow stations to monitor the strength of their signals. Because of the moment-to-moment changes in propagation that normally accompany HF transmissions, as well as the RBN's unique definition of SNR, it makes sense to see how the RBN reports known stable transmissions over time.

In this post I take the first step, and determine which stations make reasonable candidates for further investigation.

The RBN can quickly tell us which beacons are posted most frequently, simply by counting posts of stations that transmit on a single frequency over a long period. If we look at the period from the RBN's inception in 2009 to the end of 2016 (using, for example, this file), we find the following "top twenty" beacons:

Position Station Frequency (kHz) Number of Posts Earliest Post Latest Post
1 I1MMR 7026 244,964 20090308 20161231
2 I1MMR 7027 182,465 20090308 20161231
3 4U1UN 14100 167,360 20140618 20161231
4 AA1K 1821 156,091 20090221 20161231
5 SK6RUD 10133 156,067 20100720 20160421
6 4X6TU 14100 146,961 20110215 20161231
7 DK0WCY 10144 145,174 20100601 20161231
8 W9ZN 7034144,399 20090225 20161231
9 W0ERE/B 10129 141,262 20100213 20161029
10 W0ERE 10129 135,741 20091105 20161029
11 EW7LO 7008 130,706 20090221 20161231
12 4X6TU 21150 118,790 20110303 20161231
13 IK1HGI/B 7039 111,146 20120516 20161231
14 YV5B 14100 107,564 20131228 20161231
15 DJ6UX 7037 101,942 20121210 20161229
16 DK0WCY 3579 97,002 20111027 20161231
17 DK7JI 7011 96,328 20100112 20161231
18 IK4VFD 7027 94,317 20091130 20161231
19 4X6TU 18110 92,867 20120127 20161231
20 CT1ZQ 7010 91,997 20090301 20161227

Notes:
  1. Frequencies are rounded to the nearest kHz;
  2. The first two positions are occupied by what is really the same station, which appears to transmit on 7026.5 kHz;
  3. Positions 9 and 10 appear to be occupied by a single station, using alternative versions of a single callsign;
  4. I am unsure how the U.S. stations in the list can be legal, since the FCC's regulations appear to limit [unattended] HF beacons to a portion of 10m;
  5. FCC regulations also appear to disallow the use of the "/B" indicator as used by station number 9, as the B series is allocated to China.
  6. It is my memory that the original HF beacons were all located on 28 MHz, so that listeners could be made aware of an opening. It is noticeable that not a single one of the stations on the list above is on 10m: the vast majority are on bands that can reasonably be expected to support some kind of non-local propagation at almost all times (which is probably the very reason that they are posted by the RBN so often -- but one does wonder what the putative purpose of such a beacon is);
  7. Of the twenty stations in the list, all but five were still active as of the end of 2016.

2017-02-13

Compressed Archive of LANL GPS Charged-Particle Data

Recently, the National Oceanic and Atmospheric Administration (NOAA) made available to the public a 16-year dataset of measurements of the charged-particle environment at 23 GPS satellites prepared  by the Combined X-Ray Dosimeter (CXD) team at Los Alamos National Laboratory. The dataset comprises a hierarchy of directories that total about 65 GB in size. As the dataset is uncompressed, I have made available a tarred, compressed mirror of the dataset, which is about 5.7 GB in size. This mirror has the MD5 checksum: 443c5787665a9ff7456ca037101b72e0. All the files in the original LANL release are contained in the mirror, without change.
The basic documentation for the dataset is contained in a README file; the following description of the data is taken from that file:

For all satellites except Space Vehicle Navstar (SVN) numbers 41 and 48, the data are:

Variable name type Dim. description
decimal_day
double


1 GPS time, a number from 1 (1-Jan 00:00) to 366 (31-Dec 24:00) or 367 in leap years.
Geographic_Latitude double 1 Latitude of satellite (deg)
Geographic_Longitude double 1 Longitude of satellite (deg)
Rad_Re double 1 (radius of satellite)/Rearth
rate_electron_measured double 11 Measured rate (Hz) in each of the 11 CXD electron channels
rate_proton_measured double 5 Measured rate (Hz) in each of the 5 CXD proton channels (P1-P5)
LEP_thresh double 1 LEP threshold in E1 channels (0 means low, 1 means high)
collection_interval double 1 dosimeter collection period (seconds)
year int 1 year (e.g. 2015)
decimal_year double 1 decimal year = year + (decimal_day-1.0)/(days in year)
SVN_number int 1 SVN number of satellite
dropped_data int 1 if =1 it means something is wrong with the data record, do not use it
b_coord_radius double 1 radius from earth's dipole axis (earth radii)
b_coord_height double 1 height above the earth's dipole equatorial plane (earth radii)
magnetic_longitude double 1 Magnetic longitude (degrees)
L_shell


double 1 L_shell (earth radii) – currently this is the same as L_LGM_T89IGRF but this is intended to be our suggested choice for the L shell calculation in the long run.
L_LGM_TS04IGRF double 1 LanlGeoMag L-shell McIlwain calculation, TS04 External Field, IGRF Internal Field.
L_LGM_OP77IGRF double 1 LanlGeoMag L-shell McIlwain calculation, OP77 External Field, IGRF Internal Field (not currently filled)
L_LGM_T89CDIP double 1 LanlGeoMag L-shell McIlwain calculation, T89 External Field, Centered Dipole Internal Field
L_LGM_T89IGRF double 1 LanlGeoMag L-shell McIlwain calculation, T89 External Field, IGRF Internal Field
bfield_ratio double 1 Bsatellite/Bequator
local_time double 1 magnetic local time (0-24 hours)
utc_lgm double 1 UTC (0-24 hours)
b_sattelite double 1 B field at satellite (gauss)
b_equator double 1 B field at equator (on this field line I think) (gauss)
electron_background double 11 estimated background in electron channels E1-E11 (Hz)
proton_background double 5 estimated background in proton channels P1-P5 (Hz)
proton_activity int 1 =1 if there is significant proton activity
proton_temperature_fit


double 1 characteristic momentum -- R0 in the expression given above (MeV/c)
proton_density_fit double 1 N0 parameter in fit to proton flux ((protons/(cm2 sec sr MeV))
electron_temperature_fit


double 1 electron temperature from a one Maxwellian fit (MeV)
electron_density_fit double 1 electron number density from a one Maxwellian fit (cm-3)
model_counts_electron_fit_pf double 11 E1-E11 rates due to proton background based on proton flux fit -- currently not filled (all -1's)
model_counts_proton_fit_pf double 5 P1-P5 rate from proton fit (using proton_temperature_fit, proton_density_fit)
model_counts_electron_fit double 11 E1-E11 rates from the 9-parameter electron flux model
model_counts_proton_fit double 5 P1-P5 rates from electron background -- currently not filled (all -1's)
proton_integrated_flux_fit double 6 integral of proton flux (based on fit) above 10, 15.85, 25.11, 30, 40, 79.43 MeV (proton kinetic energy)
proton_flux_fit


double 31 intended to be proton flux at 31 energies, not filled currently
proton_fluence_fit double 6
not filled currently


integral_flux_instrument


double 30 (based on 9 parameter fit) integral of electron flux above integral_flux_energy[i] particles/(cm2 sec)
integral_flux_energy double 30
energies for the integral of integral_flux_instrument (MeV)


electron_diff_flux_energy double 15 energies for the fluxes in electron_diff_flux_energy (MeV)
electron_diff_flux double 15 (based on 9 parameter fit) electron flux at energies electron_diff_flux[i] (particle/(cm2 sr MeV sec))
Efitpars double 9 fit parameters for 9 parameter electron fit
Pfitpars double 4 Fit parameters for 4 parameter proton fit. These are still a work in progress. The parameters are here as placeholders until we finalize the fit function and parameters.
 
 
For SVN numbers 41 and 48, the data are:


Variable name type Dim. Description
decimal_day
double


1 GPS time -- a number from 1 (1-Jan 00:00) to 366 (31-Dec 24:00) or 367 in leap years
Geographic_Latitude double 1 Latitude of satellite (deg)
Geographic_Longitude double 1 Longitude of satellite (deg)
Rad_Re double 1 (radius of satellite)/Rearth
rate_electron_measured double 8 Measured rate (Hz) in each of the 8 BDD electron channels (E1-E8)
rate_proton_measured double 8 Measured rate (Hz) in each of the 8 BDD proton channels (P1-P8)
collection_interval double 1 dosimeter collection period (seconds)
year int 1 year (e.g. 2015)
decimal_year double 1 decimal year = year + (decimal_day-1.0)/(days in year)
svn_number int 1 SVN number of satellite
dropped_data int 1 if =1 it means something is wrong with the data record, do not use it
b_coord_radius double 1 radius from earth's dipole axis (earth radii)
b_coord_height double 1 height above the earth's dipole equatorial plane (earth radii)
magnetic_longitude double 1 Magnetic longitude (degrees)
L_shell


double 1 L_shell (earth radii) -- I do not clearly understand the origin of the calculation, but it seems to be a dipole field/T-89
bfield_ratio double 1 Bsatellite/Bequator
local_time double 1 magnetic local time (0-24 hours)
b_sattelite double 1 B field at satellite (gauss)
b_equator double 1 B field at equator (on this field line I think) (gauss)
Diffp double 1 No longer used
sigmap double 1 No longer used
electron_background double 8 estimated background in electron channels E1-E8 (Hz)
proton_background double 8 estimated background in proton channels P1-P8 (Hz)
proton_activity int 1 =1 if there is significant proton activity
electron_temperature double 1 electron temperature from a one Maxwellian fit (MeV)
electron_density_fit double 1 electron number density from a one Maxwellian fit (cm-3)
model_counts_electron_fit double 8 E1-E8 rates from the 2-parameter Maxwellian fit to the electron data
dtc_counts_electron double 8 Dead time corrected electron rates (from data, not fit)
integral_flux_instrument


double 30 (based on 2 parameter Maxwellian fit) integral of electron flux above integral_flux_energy[i] particles/(cm2 sec)
integral_flux_energy double 30 energies for the integral of integral_flux_instrument (MeV)
electron_diff_flux_energy double 15 energies for the fluxes in electron_diff_flux_energy (MeV)
electron_diff_flux double 15 (based on 2 parameter Maxwellian fit) electron flux at energies electron_diff_flux[i] (particle/(cm2 sr MeV sec))


Notes (confirmed with the CXD team):
  1. Some of the data are given in terms of Earth radii. For the purposes of those measurements, the Earth is assumed to be a sphere of radius 6371 km.
  2. A record's timestamp is the time of the centre of the collection interval.
  3. Magnetic local time is defined as the difference (in units of time, where 24 hours is equivalent to 360°) between the magnetic longitude of the record and the magnetic longitude of the anti-solar point at the time of the record.