pNav

The pNav GPS receiver project began in 2013. My doctoral student, Ondrej Jakubov, proposed using a Witch Navigator for positioning the small satellite. The CubeSat project started at the Czech Technical University in Prague as a student initiative. The student planned to participate in the QB50https://cordis.europa.eu/project/id/284427/reporting CubeSat constellation competition. I appreciated this initiative, as our university has launched a new aerospace study program in which I was responsible for teaching radio navigation and radio communication topics.

Unfortunately, we have not received any support for the satellite project, and the student team has consequently disbanded. There are only two people left, Jaroslav Laifer and me. We continue with a CubeSat project at our own expense. The project has resulted in the successful launch of the Lucky 7 CubeSat in June 2019.

The Witch Navigator was a research of dual-frequency GNSS receiver designed as a PCMCIA card for a PC. Witch Navigator is absolutely incompatible with a 1U CubeSat platform!

At that time, I had defined the following high-level requirements on the new navigation receiver for a CubeSat that I respected for all years of development of the pNav receiver:

• The CubeSat navigation receiver should be as simple as possible and integrate all necessary parts for navigation in the LEO Orbit
• It should be compatible with a 1U CubeSat platform, ie, power consumption should be a fraction of the power budget of 1U satellite. The receiver should be small and light.
• The applied signal and measurement processing algorithms should be simple and very robust

pNav receiver was developed from the beginning as a private and private founding project at my private laboratory in our house. The receiver is marketed by the company SkyFox of Jaroslav Laifr.

The main milestones of pNav development:

• 2016: Introduction to the market - GPS L1 C/A receiver with the 15 GPS L1 E-L correlators. Serial acquisition based on N of M algorithm. The typical receiver's start time was 300 seconds.

• 2017: Acquisition unit The problem of the pNav receiver from the beginning till the introduction of pNav2 is a problematic cold start and restart after position loss. The partial solution was the introduction of DSP acquisition unit, that can investigate the whole search range in Dooper frequency and code delay for all 32 satellites within 20s. Unfortunately, due to technological limitations of hardware manufacrure we cannot use an FPGA with enough performance to run GPS correlators and aqusition unit simultaneously. So the receiver frstly configure FPGA by an qausition unit. After it finishes the signal processing, the FPGA is reprogrammed by a GPS correlatos. The information from the acquisition unit is used for the acceleration of the receiver cold start. Under the ideal conditions, the receiver's cold start was shortened to 60 - 70 seconds. But this receiver configuration does not allow the DSP requisition if the signal or position is lost.

• 2018: Buying a implementation of a GPS software simulator ReGen by IPSolutios.

• 2022: Application of the orbital position propagator with the aim of overcoming GPS position dropout and improving the receiver reacquisition.

• 2026: Last update of the original pNav of Almanach memory

• 2026: Introduction of pNav2

Further development of pNav is not possible without upgrading the acquisition unit, which will work in parallel with GPS correlators.