Teams using CubeSats will have to balance a number of considerations. Getting to a destination under a CubeSat’s own power will demand that much of the craft’s weight be dedicated to propulsion and fuel. Alternatively, hitching a ride on a larger spacecraft requires a big mission to already be going in the right direction. Furthermore, a CubeSat attached to a larger mission would take up space that could be used to house, for example, an additional instrument.Nonetheless, Sayanagi sees potential in small spacecraft that detach from larger missions to gather additional measurements that would otherwise be impossible. For example, his concept calls for a small probe to dive into the atmosphere of an outer planet, without requiring the larger spacecraft that carried it there to do the same. Sayanagi thinks it’s unlikely that a CubeSat could make it to an outer planet on its own anytime in the near future. If small spacecraft hitch rides with larger spacecraft, however, the communication and power challenges involved go “from the impossible to the possible,” he says.When they can fly solo, CubeSats and other small satellites could have a major impact on space science by filling in key gaps in data. For example, Valeria Cottini, an associate research scientist at the University of Maryland and principal investigator for the CubeSat UV Experiment, is working on a mission concept for a CubeSat that would travel to Venus to investigate its atmosphere. For decades, planetary scientists have wrestled with questions about mysterious stripes that appear in Venus’s cloud layer when viewed in ultraviolet. Waiting for the next big mission to Venus could mean going without new data for 10 years or more. But Cottini’s CubeSat concept would provide a relatively cheap and feasible way to fill in information on the venusian cloud tops. In general, she says, CubeSats could be complementary to larger missions and enable science that would otherwise be impossible due to time, money, or risk constraints.“One of the holy grail things about a [CubeSat] is taking advantage of launching multiple units,” says JaeSub Hong, an instrument scientist and Harvard astronomer. Hong is deputy principal investigator for CubeX, a mission concept that would use a small spacecraft equipped with an X-ray telescope to scan exposed material in impact craters on the Moon. Measuring the elemental composition of these deep-seated materials could help scientists better understand the evolution and early history of the Moon. A small spacecraft may not be able to scan the complete surface of the Moon, but Hong points out that making a second or third after building the first one would be relatively easy. “It could be possible to extend, expand, or enhance the mission in a gradual fashion,” he says.Hong notes that, while such a spacecraft could theoretically investigate asteroids and other airless bodies, the team decided to first aim for the more achievable goal of going to the Moon. “I thought going to the Moon would be easy by now, but it isn’t,” Hong says. “It may be easier than other distant targets, but it’s still very hard.”However, despite the challenges, some of the next CubeSats to go beyond Earth orbit will be headed for the Moon. The Exploration Mission 1 (EM-1) — which is the first launch scheduled for NASA’s new Space Launch System in 2020 — will carry 13 CubeSats, including several built by student and amateur teams.