ASTRONAUT’S VIEW | ASTEROID EXPLORATION An asteroid companion A newly discovered asteroid will orbit in loose formation with Earth for centuries. Its presence reminds NASA exploration planners of attractive opportunities for robotic and human exploration as they examine varied paths toward deep space and Mars. By Tom Jones | [email protected] | www.AstronautTomJones.com University of Hawaii’s Panoramic Survey n April, astronomers sifting through preparation for journeys to Mars. A skeptical Con- Telescope & Rapid Response System in April images from the University of Hawaii's gress seems unwilling to fund NASA's proposed As- detected a near-Earth Panoramic Survey Telescope & Rapid teroid Redirect Mission, a crewed mission to an as- asteroid, designated Response System in Maui discovered a teroid fragment placed in lunar orbit. HO3 and 2016 HO3, that has faint near-Earth asteroid, now desig- other, even more accessible asteroids may serve as been orbiting in Earth’s natedI 2016 HO3. Analysis of its orbit soon alternate destinations: far enough beyond the celestial backyard for almost a century — showed that the 50- to 100-meter-wide object moon to test astronauts on a multi-month, deep- and will be around for circles the sun on a path very much like Earth's, space expedition, but not nearly as challenging and centuries longer. flying formation within a few million miles of risky as a full-up, multi-year journey to the red our planet for at least the next century. planet. A reasonable path toward Mars may take The discovery of HO3 underscores the practi- astronauts from a lunar orbit outpost, to one or cal possibility of exploring nearby asteroids as a more near-Earth asteroids, and then to the Mars way to gain valuable deep-space experience in system in the 2030s. 12 | SEPTEMBER 2016 | aerospaceamerica.com Rob Pat Ratkowski Rawlings Because of HO3's relative proximity, we refer to get astronauts out beyond the moon in the 2020s or to it as a quasi-satellite of Earth, Paul Chodas, man- early 2030s, either HO3 or another attractive target is ager of NASA's Center for Near-Earth Object Studies nearly always within range. at the Jet Propulsion Laboratory in Pasadena, Cali- fornia, said in an article on nasa.gov. Our calcula- Sifting the skies tions indicate 2016 HO3 has been a stable quasi-sat- HO3's discovery resulted from NASA's ongoing sur- Upper right: This painting ellite of Earth for almost a century, and it will vey of the inner solar system for potentially hazard- by artist Pat Rawlings continue to follow this pattern as Earth's companion ous objects. Since 1998, when Congress directed shows astronauts for centuries to come. NASA to search for near-Earth objects such as com- exploring a near-Earth asteroid. Asteroids As HO3 alternately races ahead of and falls be- ets and asteroids large enough to cause global could serve as alternate hind Earth in its yearly trek around the sun, it damage if they struck Earth, the space agency has destinations to Mars ranges out to about 100 times the moon's distance, been funding a growing array of dedicated search and provide deep-space then closes to as few as 38 lunar distances: from 38 telescopes and the astronomers who operate them. experience. million down to 14.7 million kilometers. Today, the NASA search program's $50 million an- Other asteroids make closer approaches to Earth, nual budget covers search, orbit cataloging, asteroid and can be reached with less rocket propellant. But deflection research and spacecraft mission defini- what makes HO3 special is that it's always around for a tion. It also identifies candidate targets for NASA's visit: It offers a launch opportunity every year for the planned Asteroid Redirect Mission, ARM, in which next few decades. Other typical near-Earth asteroids robotic spacecraft would lift a 10- to 20-ton boulder offer only periodic, infrequent launch windows. HO3's from an asteroid and nudge the fragment into lunar discovery is a timely reminder to NASA that if it wants orbit. Once stabilized there, an Orion astronaut crew aerospaceamerica.com | SEPTEMBER 2016 | 13 ASTRONAUT’S VIEW | ASTEROID EXPLORATION Paul Chodas/Jet Propulsion Laboratory Propulsion Chodas/Jet Paul Earth to Sun Left: Asteroid 2016 H03 has been orbiting the would rendezvous with the object, examine it, and sun in near proximity to Earth for decades. For an carry samples to Earth. NAMING ASTEROIDS observer looking down NASA-funded telescopes are discovering close An asteroid’s initial designation is on Earth as it orbits the to 2,000 near-Earth objects each year; the program assigned by the Minor Planet Center sun, the blue lines track has found 98 percent of the nearly 15,000 of those following a formula based on the year the asteroid’s movement of discovery, two letters and, if need be, cataloged so far. NASA today is working to fulfill a relative to Earth between further digits. 2016 HO3, for example, 1960 and 2020. 2005 congressional mandate to find asteroids capa- was discovered in 2016, in the second ble of causing regional damage on Earth, meaning half of April (H), and was the 90th object those 140 meters or larger in diameter. It has already discovered in the latter half of April (O3). cataloged an estimated 95 percent of those larger objects (based on near-Earth object population sta- tistics and the rate at which search telescopes “re- stead. With ARM, astronauts could visit an asteroid Center: Artist’s rendering discover” known objects). As of July 13, 1,714 ob- fragment delivered to lunar orbit no earlier than 2026, of Asteroid Redirect jects in the catalog — some 12 percent — were but NASA would still fulfill the presidential asteroid Mission, NA SA’s proposed termed “potentially hazardous,” capable of colliding directive, after a fashion. crewed mission to an asteroid fragment placed with Earth in the distant future. None poses a signifi- Does HO3 offer NASA a new, game-changing as- in lunar orbit. Congress cant threat of impact within the next century. teroid target? Veteran astrodynamicist and former seems unwilling to fund NASA Johnson Space Center flight dynamics officer the mission, providing Accessible asteroids Dan Adamo told me in an email that although 2016 impetus to send HO3 joins dozens of other known near-Earth aster- HO3 has long-term proximity going for it, it’s hardly astronauts to nearby asteroids instead. oids, NEAs, accessible to human explorers. NASA fil- the most attractive target out there. Writes Adamo: ters NEA discoveries through its NEO Human Space- “As of July 11, 2016, a total of 1765 NHATS-compliant flight Accessible Targets Study, or NHATS, identifying near-Earth objects was known. Of these, 566 near- objects whose orbits make possible roundtrip expedi- Earth objects can be accessed with shorter round-trip tions by robots or humans in 450 days or less, and a durations than any 2016 HO3 mission. Likewise, 184 total mission velocity change, rV, of 12 kilometers per NHATS-compliant near-Earth objects can be ac- second or less (think of rV as a stand-in for how much cessed with less delta-V than any 2016 HO3 mission.” rocket fuel you’ll need to fly the mission). President In fact, HO3’s orbital tilt, or inclination, of 7.77 de- Obama set a goal of an astronaut expedition to an as- grees imposes a significant velocity-change penalty on teroid in its native, solar orbit by mid-2020s. But when visiting spacecraft. By contrast, the NEA 2000 SG344 it became evident under the president’s budgets that has an inclination of just 0.11 degrees, yielding a mini- the combination of Orion, the Space Launch System mum mission velocity change of 3.56 kilometers per booster, deep-space propulsion and a habitation second, according to Adamo. In 2029, for example, a module would not be ready by the end of the 2020s, five-month roundtrip to SG344 requires a velocity NASA proposed the Asteroid Redirect Mission in- change of only about six kilometers per second. 14 | SEPTEMBER 2016 | aerospaceamerica.com NASA Dan Durda/Southwest Research Institute Research Dan Durda/Southwest Right: Rendering of a near-Earth asteroid. Nevertheless, HO3's loitering behavior makes it size of Carl Sagan's pale blue dot. Supply consider- A handful of asteroid a regularly accessible exploration target a launch ations are daunting, too: a crew of four would need candidates exist that window to it is always handy. In any given year, for to pack almost 2.5 metric tons of food for a one-year astronauts could reach example, a 154-day round trip to HO3 could be asteroid roundtrip. in the next two decades mounted for a total velocity change of roughly 12 ki- Still, an asteroid expedition would be less chal- at a lower propellant cost than going to the lometers per second. Stretching the mission dura- lenging in terms of time, distance, and logistics than lunar surface. tion to one-year reduces the velocity change to 6.1 the two-plus-year journey to the Martian moons and kilometers per second significantly less than back. An NEA mission could offer NASA just the landing that same spacecraft on the moon, which right-sized first step on the road to Mars. takes about 9 kilometers per second. Both HO3 mis- sions would include eight days of surface explora- Carpe diem tion time at the asteroid. More accessible NEAs like HO3 and SG344 will be found in the coming decade, offering NASA more Where next Ð if anywhere? asteroid targets of opportunity. NASA could team Although far from the optimum candidate, HO3's with robotic mining companies to send small ro- discovery in our celestial backyard keeps asteroids, botic scouts to a promising few.