## 1 Introduction
Performing in situ measurements of waves in ice is, however, a challenging and costly operation. Commercial instruments have traditionally been extremely expensive, and sometimes of varying quality, with typical prices after taxes in the 7.5-50 kUSD range. The situation became somewhat better with the emergence of new actors, such as Sofar and their Spotter buoy [46], which took down the price to a typical 6-8 kUSD cost per instrument, once import taxes and satellite communication fees were factored in. Still, the Sofar Spotter, while gaining from being a very modern as well as relatively low-cost design, is not very well-adapted for use in the polar regions, as it was designed primarily for measuring open water wave statistics and, correspondingly, relatively large waves. In particular, its battery life limits the duration of deployments in the polar night [43]. In addition, its GPS-based wave measurement method, while having many advantages in open water (such as accurate directional wave spectrum measurement), has significantly higher noise for the typically small waves observed in the ice than what can be achieved with a modern Inertial Motion Unit (IMU). As a consequence of these challenges, a number of groups have developed in-house, custom instrumentation for measurements of waves in ice (e.g., [40; 41; 47]. A very brief overview is provided in Figure 1. This is, in our opinion, a situation that is so far quite inefficient. Indeed, a number of groups develop their own closed-source solution, in parallel of each other, wasting a large amount of engineering resources in the form of working hours and prototyping costs in the process. An increasingly promising direction is the development of open-source instrumentation, which allows to both reduce hardware costs and mutualize the instrumentation development workload. This approach was recently adopted by [PERSON] et al. [51] and, since its development in 2015, has undergone several updates (the full lineage of our series of open-source instruments is presented in Figure 2). In the following, we will refer to the design described in [PERSON] et al. [51] as the \"v2018 instrument\" or \"v2018\" in short. Since the initial deployment of the first v2018 instruments [PERSON] et al. [51], the low-cost and open-source fundament of the instrument has promoted usage and international collaboration across the world. The v2018, and adaptations thereof, have been deployed in both the Arctic and Antarctic to study sea-ice drift [52], wave attenuation and dispersion [19], and wave-induced sea ice break-up [14]. Through these collaborations and technological  
Figure 1: Overview of waves in ice instruments, distinguishing between (i) commercial instruments, (ii) closed-source instruments, (iii) open source. Commercial instruments have been available for a long time, in particular the Datawell Waverider series of instruments (**1**), which goes back all the way to the 1960s [48]. More recently, the Sofar Spotter (**2**) has become a viable, lower-cost alternative, though there are a number of limitations, particularly regarding battery autonomy [49] and the price. A number of groups have developed satellite-connected autonomous instruments that have been described in research articles, but that remained closed source. A few instruments we know about were released in 2006 (**3**) [47; 50], 2016 (**4**) [40], and 2021 (**5**) [24]. By contrast, our group has decided to release our designs as open source, so that they can be freely used and improved by other groups, starting in 2018 (**6**) [51] and now with the present design (**7**). advancements, points of improvement were identified, which supported advancement of the v2018 and development of the latest \"v2021\" version. These challenges of high instrumentation costs and the need for more in situ ground truth data are not specific to the waves in ice community.