# Contrails and Their Dependence on Meteorological Situations
## Appendix A  
After decoding the signal, it is possible to obtain the 24-bit ICAO address of the aircraft from each Mode S response. Depending on the descriptor (the first 5 bits of the Mode S message, the DF field) the message contains the barometric altitude or aircraft identification or the ICAO aircraft address (DF4) in the case of a short 56-bit response, DF5, DF11); in the case of a long 112-bit response, the message contains the barometric altitude (DF20) or identification (DF21); and in the 56-bit MB field, the contents of the BDS register requested by the responder. In DF20 and DF21 messages, the MB field may carry true track angle, TAS, and ground speed (GS) from the BDS 5.0 register, or magnetic heading, indicated airspeed, Mach number, and inertial vertical velocity from the BDS 6.0 register, or wind speed, wind direction, static air temperature, average static pressure, turbulence, and humidity from the BDS 4,4 register, or turbulence, windshear, microburst, icing, wakevortex, static air temperature, average static pressure, and radio height from the BDS 4,5 register. In FIR Praha, the BDS 4,5 register is not requested and very few aircraft respond to a request for a BDS 4,4 register extract. Generally, support for this register is not mandatory. The Mode S message with DF17 carries an ADS-B broadcast, each message containing the ICAO 24-bit aircraft address and a 56-bit ME field listing one of the mandatory supported BDS registers. In the ME field, among others, the airborne position (latitude and longitude of the WGS84 coordinate system with barometric or GNSS altitude indication) from the BDS 0,5 register or ground speed/airspeed and heading, vertical rate, and GNSS/geometric height difference from the baroaltitude from the BDS 0,9 register may be transmitted. Thus, for a particular aircraft forming a contrail within the range of a 1090 MHz receiver, quite a lot of information about the aircraft can be assigned from the SSR and ADS-B systems, but in most cases, there is no measured information about the environment around the aircraft. * ICAO [2008] ICAO. _Doc 9871: Technical Provisions for Mode S Services and Extended Squitter_, AN/464, 1 st ed. ; ICAO: Montreal, QC, Canada, 2008; ISBN 978-92-9231-117-9. * Radiosonde [2020] Radiosonde RS41-SG Datasheet. Vaisala. 2020. Available online: [[https://docs.vaisala.com/v/u/B211321](https://docs.vaisala.com/v/u/B211321) EN-K/en-US]([https://docs.vaisala.com/v/u/B211321](https://docs.vaisala.com/v/u/B211321) EN-K/en-US) (accessed on 15 January 2024). * Aeronautical Information Publication of the Czech Republic. AIP ENR 5.3-1. Available online: [[https://aim.rlp.cz/ais_data/aip/data/valid/e5-3.pdf](https://aim.rlp.cz/ais_data/aip/data/valid/e5-3.pdf)]([https://aim.rlp.cz/ais_data/aip/data/valid/e5-3.pdf](https://aim.rlp.cz/ais_data/aip/data/valid/e5-3.pdf)) (accessed on 20 January 2024). * The Scilab Consortium [2023] The Scilab Consortium. Scilab. Available online: [[http://www.scilab.org](http://www.scilab.org)]([http://www.scilab.org](http://www.scilab.org)) (accessed on 3 September 2023). * [PERSON] et al. [2007] [PERSON]; [PERSON]; [PERSON]; [PERSON] _Fyzikozhakai a Snzek_; Academia: Prague, Czech Republic, 2007; pp. 105-118. * _Doc 7488/3_; Manual of the ICAO Standard Atmosphere. International Civil Aiation Organization (ICAO): Montreal, QC, Canada, 1993. * [PERSON] [2023] [PERSON] A Piecewise Linear Regression and Classification Algorithm with Application to Learning and Model Predictive Control of Hybrid Systems. _IEEE Trans. Autom. Control_**2023**, _68_, 3194-3209. [CrossRef]
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