# HYPSO-1 CubeSat: First Images and In-Orbit Characterization
## 2 Mission and Payload Operations
### Operations Workflow  
The planning and operational tools have to a large extent been developed during the payload commissioning and operational phases. The HYPSO project has established a digital agile-inspired workflow that allows for continuous incremental development and live tests. During the first weeks of payload commissioning, the imaging schedule scripts were written, uploaded to, and downlinked from the satellite manually. While the tools were developed further and built-in functions from the Mission Control System (MCS) were utilized more, automation of scripts and upload/download tasks became possible. As with most optical sensors, the HYPSO-1 hyperspectral sensor is hindered by clouds. By requiring a forecast of a cloud-free scene, the number of viable acquisitions over areas of interest becomes very limited. Furthermore, the high revisit time through pointing can to some extent give more capture possibilities over the same area with a shorter revisit time, reducing the impact of clouds. It has been observed that a threshold at around 50% gives satisfactory images, as indicated in Table 2. This threshold should be changed based on the importance of mapping specific area. In general, a lower cloud coverage is of course desirable. Since the attitude of the satellite can be controlled, targets can be imaged even if the satellite is not directly above them. The elevation angle between the satellite and the target area of interest also affects the imaging quality with regard to parameter retrieval. At lower elevation angles, i.e., more off-nadir, the observations are more skewed and have a poorer spatial resolution. Additionally, adverse effects from the atmosphere are also observed. This is exhibited by blue color being more prominent in the image possibly due to Rayleigh scattering [28]. A lower limit of elevation angle is suggested in Table 2.  
The range of exposure times for HYPSO-1 is given in Table 2. The optimal values depend on the imaging scene and the solar zenith angle. The response of the imaging sensors used varies linearly with the incident light, but easily becomes saturated over clouds and deserts. As a result of this linear response, there is a trade-off between acquiring as much light over dark objects, e.g., ocean targets, and being over-exposed over brighter targets. The frame rate sets an upper bound for the exposure time. With a higher frame, the spatial resolution can also be improved, but this comes at the cost of lower exposure time. Conversely, lower exposure time can reduce SNR as less light is collected. The highest reliable frame rate for the nominal cube size can be found in Table 2.  
Satellite and imaging operations for the HYPSO-1 mission are primarily planned on a weekly basis, with smaller updates three times a week to account for weather forecasts or other events. The general workflow for the pass planning is shown from left to right, following the arrows in Figure 2. During a planning session, a prioritized list of potential targets is selected. Targets are selected based on the timing, ongoing geophysical or biological phenomena, field campaigns, weather forecast, and whether they can be observed by other agents. After all this is considered, the final observation schedule is planned and a script is generated for the next few days. The scripts are tasked for upload and execution on the satellite in the MCS, which schedules upload of the scripts to the satellite during a subsequent ground station pass. At the start time defined by the scripts, pointing is activated, the payload is powered on and an image is captured. The capture time is on the order of one minute. It should be noted that the capture time can be altered, but the data throughput is predominantly limited by the \(\approx\)1 mbit/s bandwidth of the S-band radio communication. The collected data are merged with the corresponding metadata before being transferred to the Payload Controller (PC), a designated subsystem for data storage and subsequent radio transmission onboard the satellite.