Small Satellite Exploration – Revolutionizing Science & Ready for Lift-Off
by: Cody Knipfer
When it comes to what’s next in space exploration, dream big but think small…that is, think about small satellites.
This form of spacecraft—characterized by its small size and mass—could prove to be revolutionary, transforming how we investigate our home planet and explore our solar system. Small satellites and spacecraft may usher in an exciting new era of research and discovery in space. But for huge discoveries to be made with small satellites, we will need to match their potential—both in the resources that go into them and how we decide upon their utilization.
Small spacecraft are poised to become powerful tools for space exploration for reasons that are easy to understand. Satellites are currently experiencing and benefiting from the same trends of technology miniaturization that drove revolutions in personal computers and smartphones. More “potential” can today be packed into ever-smaller platforms. The small satellites of today are often as, if not more, sophisticated and capable as large satellites of decades past.
Far cheaper to produce than their 9- or 10-figure counterparts, small satellites are changing the traditional calculus about space missions. They can be mass-produced: using common “standardized” components, small spacecraft are generally quicker to develop and manufacture. They are also much more tolerant of the inherent risks and technical challenges of spaceflight. Whereas the loss of a billion-dollar exploration spacecraft would be a major catastrophe for a space program, the loss of a small spacecraft would be acceptable, especially when the risks are compared against the tradeoff of the cost of reproduction versus the rewards of knowledge gained.
As a result, small satellites are already proving themselves as capable research tools. This is particularly evident in the commercial space sector, which has taken a leadership role in driving small satellite innovation forward. Several companies, such as Planet, are flying constellations of Earth observation small satellites which provide near-persistent coverage of changing Earth phenomena, offering valuable insights for scientists—such as monitoring weather and climate patterns, evaluating land use and erosion, and tracking animal migration.
Small satellites are also increasingly useful in civil space exploration. NASA’s Earth Venture missions, for example, include low-cost small satellite missions intended for cutting-edge Earth science. The Small Explorers program funds and flies small satellites for a range of low-cost space science missions, such as researching x-ray radiation from distant space objects, studying the interstellar boundary of our solar system, and learning more about how the Sun’s solar wind is formed. The agency’s Astrophysics Pioneers Program, established just last year, plans to fund and fly small satellites dedicated to innovative astrophysics research.
It’s not just close to home that small satellites are starting to shine. In 2018, the “Mars Cube One” (MarCO) spacecraft travelled alongside NASA’s Insight lander to Mars, providing a crucial telemetry relay back to Earth for Insight as it landed on the Martian surface. The first small spacecraft to fly to another planet, the MarCO spacecraft proved that small spacecraft could withstand the challenging environment of interplanetary space. Not only that, MarCO demonstrated that small satellites can serve important roles as “partners” for a larger mission.
NASA, recognizing that small spacecraft can have significant utility in deep space, is now planning a series of sophisticated missions with them to augment and support its lunar exploration campaign. The CAPSTONE mission, slated for launch later this year, will involve a small spacecraft entering a near-rectilinear halo orbit around the Moon, becoming the first spacecraft to do so in history. This mission will be a key pathfinder demonstration for NASA’s planned Lunar Gateway station, which will operate in the same orbit. CAPSTONE will also test novel spacecraft-to-spacecraft navigation capabilities for future use during lunar exploration missions.
The agency also intends to make full use of small satellites as part of its Artemis missions. Leveraging excess capacity aboard the Space Launch System, over a dozen small satellites are slated to piggyback a ride to lunar orbit during the rocket’s first launch. These spacecraft will conduct a variety of compelling deep-space experiments to support human activities on and around the Moon including studying the impact of deep space radiation on living organisms; identifying lunar ice deposits for future resource extraction; and testing the practicality of a cis-lunar space weather “monitoring network.”
NASA is not alone in leaning in on small satellites for space exploration. Both Italy and Japan are contributing small satellites for inclusion on the upcoming Artemis launch. A consortium of Polish academic institutions is studying a potential commercial small satellite mission to Mars. Meanwhile, the European Space Agency has five low-cost deep-space small satellite missions in development – three destined for asteroids, and two for the Moon. The most complicated of them, M-ARGO, will use advanced autonomous navigation technology to navigate itself toward a unique, little-understood class of asteroid for study.
Clearly, big opportunities and a bright future lie ahead for small spacecraft—especially for their use in novel exploration missions and architectures. There are intriguing possibilities. Imagine, for example, a constellation of small satellites around the Moon, providing near-persistent imagery and analysis of “points of interest” to astronauts exploring on the surface. Or a fleet of small satellites sent out at regular cadence to under-explored planets and locations, such as Mercury and Venus, to provide “snapshot” updates of these worlds. It is possible to envision small satellites eventually accompanying larger spacecraft to the outer planets, where they could be used to make targeted fly-bys or investigations of the many unexplored Jovian or Saturnian moons.
This is all within the realm of the achievable. But budgets and policies will need to match aspirations and visions. While there is considerable momentum toward greater use of small spacecraft for exploration, the budgets which support them remain a small fraction of overall space funding. Some NASA small satellite programs, such as the Astrophysics Pioneers Program, do not currently have the budget to fund and fly all the compelling missions proposed to them – despite each missions’ cap on the cost. Because of funding constraints, other programs, such as the Earth Venture and Small Explorers programs, only issue calls for new mission proposals once every several years. For space agencies to take full advantage of the “rapid” and risk-tolerant nature of small spacecraft, they need adequate resources and more frequent opportunities for small spacecraft development, missions, and launch.
The issue of risk is a current impediment to the more creative use of small spacecraft for novel missions or architectures—a clash between the technology’s risk-tolerant nature and the traditional risk aversion of civil space agencies. While the commercial sector has embraced risk and the potential of failure as acceptable, given small satellites’ low cost, rapid production, and re-flight rates, the same has not taken hold in the space agencies which desire absolute mission success and pristine issue-proof technology. As a result, as some reports have noted, small satellite science programs generally take too long, are more expensive than they need to be, and discourage scientists from proposing innovative or potentially risky missions. NASA would do well to relax its risk thresholds for novel small satellite missions when the potential science return is compelling compared to investment, akin to the “shots on goal” approach the agency is experimenting with its commercial lunar lander CLPS program.
Finally, there is the challenge of launch. Until recently, small spacecraft had been limited in the availability and frequency of launch opportunities, especially of “dedicated” launches to their targeted orbit or schedule. They have instead made do with “rideshare” launch, flying as “secondary” payloads on a launch dictated by the parameters and requirements of a larger, “primary” payload. While an effective method to simply get to space, rideshare launch constrains the ability for small satellites to decide on their ultimate orbit, destination, or timeline. These restrictions significantly limit the scope and sophistication of small satellite research and science. It is quite difficult, for example, to take targeted measurements of the polar icecaps if the rideshare launch opportunity puts you in orbit over only the equator.
Fortunately, a new class of launch vehicle catering specifically to small satellites called “small” rockets has emerged, with several companies now offering dedicated launch services. While agencies such as NASA have taken initial steps to fund and fly dedicated small launch missions, these have to-date been “one-off” demonstrations. Space agencies would do well to establish specific programs and funding for dedicated small launch, to “prime the pipeline” for tailored, advanced small satellite proposals and missions that would make use of them. NASA could also establish a dedicated small launch office to coordinate policy, requirements, and opportunities for dedicated launches of small satellites like it has for a rideshare with its new rideshare office.
These challenges, of course, are not insurmountable and, with a considerable amount of attention now focused on small satellites and their future, will likely be addressed. What is also undoubtedly likely is that, of the many remarkable space exploration discoveries to be had in the coming years, quite a few of them will have come from small satellites.