pNav History

The pNav GPS receiver project began in 2013. The Czech Technical University students planned to participate in the QB50https://cordis.europa.eu/project/id/284427/reporting CubeSat constellation competition at that time. My doctoral student, Ondrej Jakubov, proposed using a Witch Navigator receiver for positioning the satellite.

I appreciated this initiative, as our university launched a new aerospace study program in which I was responsible for teaching radio navigation and radio communication.

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

The Witch Navigator was a research 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 L1 receiver:

• The CubeSat navigation receiver should be as simple as possible
• It should integrate all necessary parts for navigation in the LEO Orbit, but not more
• 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 founded 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:

• 2013: Development Begins

• 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 in ideal conditions 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 the DSP acquisition unit, which can investigate the entire search range in Dooper frequency and code delay for all 32 satellites within 20 seconds. Unfortunately, due to the hardware manufacturer's technological limitations, we could not use an FPGA with sufficient performance to run GPS correlators and an acquisition unit simultaneously. So the receiver first configures the FPGA with an acquisition 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 and implementation of a GPS software simulator ReGen by IPSolutions.

• 2021: New Acquisition Unit that can operate in parallel with the correlators has been developed. It required a larger FPGA, which was beyond the manufacturer's capabilities.

• 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. This version is internally assigned as pNav 1.5. Together with the new acquisition unit, it is the first small step towards the new version pNav2.

• 2026: Introduction of pNav2

The further development of the pNav receiver requires:

• Increasing the performance of the acquisition unit, which will be available during the entire operation of the receiver.
• Increasing the robustness of the software. Consistent verification of the navigation message reception with the aim of detecting undetected errors through channel coding. Verification of the position input and output data and proper function of the position, velocity, and time algorithm.
• Development of the high-performance, low-power consumption GPS antenna suitable for CubeSats.
• Reliable positioning of the unstabilized, rotating, or spinning satellites.