## 3 Validation of the Instrument v2021
### Autonomy and Satellite Communication Test in the Arctic: February 2021 Deployment
\begin{table}
\begin{tabular}{l l l l l} \hline
**Wavemaker Signal:** & **Reported Buoy Amplitude** & **Reported Buoy** & **Frequency Bin Closest** & **Number of Cases** \\
**Amplitude, Period** & **(cm, Averaged)** & **Peak Period (s)** & **to Peak Frequency** & **Number of Cases** \\ \hline
2 cm, 16 s & 2.104 & 15.75 & yes & 4 \\
1 cm, 16 s & 1.040 & 15.75 & yes & 2 \\
0.5 cm, 16 s & 0.62 & 15.75 & yes & 2 \\
2 cm, 14 s & 1.954 & 13.65 & yes & 1 \\
1 cm, 14 s & 1.053 & 13.65 & yes & 1 \\
2 cm, 12 s & 2.022 & 12.05 & yes & 2 \\
1 cm, 12 s & 0.970 & 12.05 & yes & 2 \\ \hline \end{tabular}
\end{table} 
Table 4: A summary of wavemaker signal experiment results. The experiments included 1 and 2 cm amplitude waves for 12, 14, and 16 s periods, as well as an “extreme” test corresponding to an amplitude of 0.5 cm at a 16 s period. The mean values are reported for the multiple tests conducted. The instrument is able to accurately measure waves down to 1 cm at a 16 s period, with a corresponding typical accuracy of under 0.1 cm. For waves of amplitude 0.5 cm and period 16 s, the peak period is still correctly identified, but noise in the measurements starts to play a role, with a deviation of around 25% in the wave amplitude value reported. NABOS Expedition and Comparison with SOFAR Spotter Buoy in the Marginal Ice Zone in the Arctic: September 2021 Deployment  
The first field deployment opportunity for the full-feature instrument v2021 was the 2021 Nansen and Amundsen Basins Observational System (NABOS) expedition ([[https://uaf-iarc.org/nabos-cruises/](https://uaf-iarc.org/nabos-cruises/)]([https://uaf-iarc.org/nabos-cruises/](https://uaf-iarc.org/nabos-cruises/)), accessed on 15 January 2022), which was performed in the context of the ArCS II Japan-Russia-Canada International Exchange Program ([[https://sites.google.com/edu.k.u-tokyo.ac.jp/arcsi-iep-jrc/main](https://sites.google.com/edu.k.u-tokyo.ac.jp/arcsi-iep-jrc/main)]([https://sites.google.com/edu.k.u-tokyo.ac.jp/arcsi-iep-jrc/main](https://sites.google.com/edu.k.u-tokyo.ac.jp/arcsi-iep-jrc/main)), accessed on 15 January 2022). A v2021 instrument was assembled in a Zeni Lite drifting buoy, referred to as Zeni-v2021 in the following (see Appendix B for the buoy assembly details). This instrument was deployed alongside a commercial wave-measuring device (SOFAR Spotter drifting buoy, [[https://www.sofarocean.com/products/spotter](https://www.sofarocean.com/products/spotter)]([https://www.sofarocean.com/products/spotter](https://www.sofarocean.com/products/spotter)), accessed on 15 January 2022), referred to as SPOT-1386 in the following. The key difference of the Spotter compared with the instrument v2021 is that the Spotter measures surface displacements based on GNSS signal. On 15 September 2021, both buoys were deployed adjacent to the ice edge in the central Arctic Ocean (North of the Laptev Sea), at a location of 81.915\({}^{\circ}\) N 118.763\({}^{\circ}\) E, at around 05:05 UTC. The buoy deployment location is shown in Figure 6, which is overlaid with 0.15 and 0.80 sea ice concentration (SIC) contours based on the Advanced Microwave Scanning Radiometer 2 (AMSR2) data [62]. The two buoys drifted apart roughly 1 km within 8 h of being deployed and farther than 3 km after 24 h. Given that the ocean surface conditions near the ice edge are heterogeneous, we compared the instrument v2021 spectrum with that of SPOT-1386 following the deployment, when they were still close to each other. The buoy spectra compared generally well when the buoy distance was less than 1 km. The left panel in Figure 7 shows the buoy spectra at 08:21 15 September 2021, which corresponds to a moderate significant wave height \(H_{\rm m0}=1.62\) m. The comparison indicates that the spectra compare well when the low-frequency noise, which is typical in accelerometers, is discarded. Here, the method that was previously used in [63; 64] was applied to remove this noise from Zeni-v2021 spectra.