ordinary commercially available terrestrial solar panels (which are heavy when built into glass front panel and backing sheet + aluminum frame), made from high

ordinary commercially available terrestrial solar panels (which are heavy when built into glass front panel and backing sheet + aluminum frame), made from high efficiency monocrystalline si cells are commonly maxing out like: 60 x 6W 156mm cells = 360W STC rating 72 x 6W 156mm cells = 430W STC rating or around there. If they used triple junction GaAs cells or something exotic like you'd see on a satellite it could be something very different. The same mono Si cells could be used in something built to be fragile and light weight for attaching to a giant balloon. If it's something thin film the efficiency is probably less.