D-TECT: SolPol measurements

National Observatory of Athens, ReACT & University of Hertfordshire - SolPol Solar Polarimeter

PIs: Dr. Vassilis Amiridis (vamoir@noa.gr), Prof. William Martin (w.e.martin@herts.ac.uk)
co-PI: Vasiliki Daskalopoulou (vdaskalop@noa.gr), Alexandra Tsekeri (atsekeri@noa.gr)

Database distribution under CC-BY-SA (CC) rights
GitHub:  @NOA-ReACT/SolPol

Each data folder includes the following for the individual locations of operation:

- `Data_Antikythera`:
folder containing all the raw .txt data acquired by SolPol when installed in the PANhellenic Geophysical Observatory of Antikythera - PANGEA, Greece
measurement period: September 2018 to March 2022
location: lat = 35.86099, long = 23.30982,alt = 193

\txt: data acquired with default instrument aperture size (@5.5mm) labeled as pol_DDMMYYYY_HHMM(in UTC)_antik_duration.txt

\txt_iris: data acquired with different aperture sizes (@4.5mm, 5.5mm and 7mm) labeled as polirisXX_DDMMYYYY_HHMM(in UTC)_antik_duration

\txt_dark: closed aperture dark measurements labeled as poldark_DDMMYYYY_HHMM(in UTC)_antik_duration, either with instrument tracker not tracking (NT index) or standard tracking (T index)

- `Data_Athens`:
folder containing all the raw .txt data acquired by SolPol when installed in the National Observatory of Athens (NOA), Athens, Greece
measurement period: 18/04/2020 to 14/05/2020
location: lat = 37.966295, long = 23.710624,alt = 60

\txt: data acquired with default instrument aperture size (@5.5mm) labeled as pol_DDMMYYYY_HHMM(in UTC)_ath_duration.txt

- `Data_Cyprus`:
folder containing all the raw .txt data acquired by SolPol for the duration of the preliminary ASKOS 2019 campaign, in the Cyprus Institute - Nicosia, Cyprus
(lat = 35.14063, long = 33.38135,alt = 181)

\txt: data acquired with default instrument aperture size (@5.5mm) labeled as pol_DDMMYYYY_HHMM(in UTC)_cyp1_duration.txt

- `Data_Mindelo`:
folder containing all the raw .txt data acquired by SolPol for the duration of the ASKOS 2022 campaign, in the Ocean Science Centre Mindelo (OSCM) - Mindelo, Cape Verde
(lat = 16.87775, long = -24.994889,alt = 20)

\txt: data acquired with default instrument aperture size (@5.5mm) labeled as poliris55_DDMMYYYY_HHMM(in UTC)_mndl_duration.txt

\txt_dark: closed aperture dark measurements labeled as poldark_DDMMYYYY_HHMM(in UTC)_mndl_duration

## Text file Header

The raw data `header` is:

SOLAR POLARIMETER

1. `Polarimeter Position [deg]`:
Instrument rotational position at 0 and 45 degrees from reference

2. `Rotator Position [deg]`:
Polarizer position in sets of [0, 40, 130, 220, 310] in degrees

3. `PEM Setting [nm]`:
Photoelastic Modulator Head operating wavelength, default 550nm

4. `Retardation [waves]`:
PEM induced retardation

5. `Wavelength Filter (Wavelength-Bandwidth)`:
Filter wheel filter selection, default 550nm

6. `ND-Filter`:
Neutral density 0.3 filter (pre-defined)

7. `Time (UTC)`:
Measurement starting time in HH:MM:SS (UTC)

8. `Bias Voltage on Diode`
Should be zero if instrument working properly, forward bias

9. `LabJack, mean DC (AIN0)`:
DC output voltage from the DAQ in Volts

10. `LabJack, other`:
State zero if instrument works properly

11. `Lock-in, 1w`:
RMS Voltage output from channel 1 of the Lock-in amplifier, signal phase on resonant frequency (ω) in degrees

12. `Lock-in, 2w`:
RMS Voltage output from channel 2 of the Lock-in amplifier, signal phase on twice the resonant frequency (2ω) in degrees

## Data validity

! Data file to be valid needs to contain **5** sets of measurements [1-12 above] for each `Rotator Position [deg]` per `Polarimeter Position [deg]`. <br />

! Every valid file stops at a `Polarimeter Position [deg]` == 45 degs & `Rotator Position [deg]` == 310.