2.And keeping the satellite's huge beam and the distant rectenna reliably synced up also stands as an unsolved technical issue.
而要使卫星发射出来的巨大微波束与地面的网格形天线一直保持同步,也是一个尚未解决的技术难题。
3.Another problem of minimality also remains unsolved—to wit, what is the smallest number of digits a puzzle maker can place in a starting grid and still guarantee a unique solution?