<?xml version="1.0" encoding="UTF-8"?>
<Instrument xmlns="https://metadata.pithia.eu/schemas/2.2" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://metadata.pithia.eu/schemas/2.2 https://metadata.pithia.eu/schemas/2.2/pithia.xsd">
<identifier>
<PITHIA_Identifier>
<localID>Instrument_Ionosonde_Digisonde256</localID>
<namespace>ldi</namespace>
<version>1</version>
<creationDate>2022-08-31T14:00:00Z</creationDate>
<lastModificationDate>2024-12-18T12:59:00Z</lastModificationDate>
</PITHIA_Identifier>
</identifier>
<name>Ionosonde: Digisonde 256</name>
<description>Digisonde 256 is the second-generation instrument in the Digisonde family of ionosondes. Total 44 units were
built in 1970-1986, including 25 Digisonde 256 and 19 DISS (Digital Ionosphere Sounding System), a version
of the same instrument for the US Air Force space weather network.</description>
<type xlink:href="https://metadata.pithia.eu/ontology/2.2/instrumentType/VerticalSounder"/>
<operationalMode>
<InstrumentOperationalMode>
<id>ionogram</id>
<name>Scanning Ionogram</name>
<description>The system steps through frequencies according to
the selected program, transmitting and coherently integrating (a full
spectrum, i.e. FFT, Doppler integration) a stream of N pulses. Just prior
to transmission on each frequency four possible operating frequencies are
monitored for interference/occupancy and the quietest is selected for the
measurement. Then a few trial pulses are transmitted to allow automatic
adjustment of receiver gain. As each coherent integration of pulse streams
in completed, the raw output (i.e. 128 color coded amplitudes representing
echoes at 128 heights) is added to the display of the developing ionogram.
After all frequency steps have been completed the raw ionogram (16 complex
Doppler lines at 256 heights and M frequency steps) is written out to a
disk file and the automatic scaling program ARTIST (Automatic Real-Time
Ionogram Scaler with True height analysis), is invoked and a file of
automatically scaled parameters is created and displayed.</description>
</InstrumentOperationalMode>
</operationalMode>
<operationalMode>
<InstrumentOperationalMode>
<id>drift</id>
<name>Drift Ionogram</name>
<description>This is similar to the Doppler Ionogram in that
higher Doppler resolution is achieved by extending the integration period.
In addition to multiplexing frequencies the receive antennas are also
multiplexed. This provides a raw data file which records the relative
phase of all Doppler lines of all echoes on the four antennas in the
receiver array, giving the angle of arrival of the individual echoes.</description>
</InstrumentOperationalMode>
</operationalMode>
</Instrument>
