Download PDF Fall Issue of The Bridge on Space Exploration September 1, 2021 Volume 51 Issue 3 Close collaboration between engineering and science has enabled marvels of space exploration over decades. Eight exemplary missions are described in this issue, conveying the excitement, challenges, and breakthroughs involved in efforts to better understand the wonders and mysteries of this solar system. Perspective: Space Science-Past to Future Thursday, September 16, 2021 Author: Louis J. Lanzerotti Dancing lights in the polar skies—and at times even over Rome, Paris, Havana, Tokyo Rocks falling to Earth from the “heavens” Strange spots on the Sun—appearing…growing…vanishing Planets racing in epicycles across the heavens Curious behaviors of the tails of comets as they fly through the solar system A multitude of colors of stars and star clusters and galaxies Mythical creatures mapped from celestial star groupings These and numerous other phenomena in the sky have been observed and puzzled over by humans on planet Earth for millennia. The concept of “science,” arising more than 500 years ago, provided a (sometimes tortuous) path to more quantitative knowledge of such phenomena. Over time human culture advanced to seek empirical confirmation of previously purely philosophical hypotheses about the nature of celestial spectacles. Early Scientific and Technical Motivations In the early 19th century use of the electrical telegraph spread quickly in Europe and the United States following its invention and patent by Samuel F.B. Morse. But strange and episodic currents flowed in, and sometimes disrupted, this first electrical technology. These currents became a huge challenge to engineers in the latter half of the 19th century. A seeming association of the telegraph currents with the occurrence of auroras—and even with activity seen on the Sun—was reported, prompting scientists to attempt to understand a possible coupling (besides visual light) between the Sun and Earth’s environment. In the late 1890s and early 1900s Guglielmo Marconi was successful in his technological embodiment of the theoretical ideas of James Maxwell and Heinrich Hertz. He established a successful business of wireless communications, including ship-to-shore and across the Atlantic. Scientific research, experimental and theoretical, closely followed to understand why the wireless waves did not fly off rectilinearly into space. The commercial uses and the parallel science both quickly found that the Sun had large effects on the propagation of these wireless signals, affecting the medium that was producing the signals’ reflection in Earth’s upper atmosphere. The engineered telegraph and wireless systems demonstrated early the effects on technologies of what is now called “space weather.” And these effects impelled science to study phenomena above Earth’s surface—beyond the astronomy that humans had pursued for millennia. Mid-20th Century Rocketry in one form or another has been attempted for centuries, motivated by both peaceful and military objectives. Rocketry for exploration—human and robotic—is of more recent vintage. Explorer 1, placed in orbit in January 1958 by a modified Jupiter-C, required a science payload. James Van Allen’s Geiger tube detector was ready, was flown, and demonstrated that the space environment that Arthur Clark and John Pierce had anticipated for their communication satellites (1945, 1955) was not benign (and it would not have been benign for Lyman Spitzer’s previously envisioned large space telescope in 1946). But the engineering achievement of placing science instruments above the atmosphere had begun—and with it awareness of the importance of space weather in space engineering. The opportunities for science opened by the engineering achievements of access to space stimulated great imaginations. Flown instruments significantly increased in number and sophistication for studies of Earth’s space environment, including the interplanetary medium. Data were needed to better understand the role of space weather for science and for human exploration. The Sun, essential for life on Earth and as the producer of space weather phenomena, spurred the invention and development of ever more capable space-based solar telescopes. Exciting Research since ‘the Eagle Landed’ Six Apollo landings (1969–72) achieved the national imperative for humans on the Moon. Instruments were placed on Earth’s natural satellite, and astronauts returned unique samples. Analyses of those samples continue to yield new insights into the Earth’s and Moon’s history. Studies of planet Earth and of the Moon were not sufficient. Mission Ulysses (1990–2009) went far above the poles of the Sun and completed three circuits. Audacious ventures to encounter the inner planets—Mercury, Venus, Mars—were executed. Mars remains a prime science objective, with both orbiters and landers (landing on the red planet is not an easy engineering job). Was there ever life on Mars? Does life exist there even now? Minor planets, asteroids, and comets have been encountered and even landed on and sampled, shedding light on the possible origins of rocks that have fallen to Earth. The giant outer planets beckoned. For their exploration nuclear power was needed. Radiation-hardened electronics were essential. The Pioneer 10 and 11 missions (1972–97), targeted toward Jupiter and Saturn, were followed by two Voyager satellites (the last dual missions designed to mitigate the possible failure of one). Launched in 1977, the Voyagers continue to transmit data, now from beyond the edge of the solar system—Voyager 1 is at more than 150 times the Sun-Earth distance, requiring 21 hours for its dispatches to be received. Both Voyagers have returned spectacular information, including photos, about not only Jupiter and Saturn but also, by Voyager 2, distant Uranus and Neptune. Pluto achieved fame with the flyby of New Horizons (2015–16). Galileo orbited Jupiter (1995–96) and dropped a measuring probe into its atmosphere. Cassini orbited Saturn (2016–17) and deployed a lander on its moon Titan. Measurements from both missions defined the dynamic space environments around the planets. Both missions also yielded tantalizing hints of where life might be hiding in the moons. The Kepler space telescope (2009–18) confirmed humanity’s speculations over the eons: A vast number of planets orbiting stars do exist. The pale blue dot of Earth, imaged from beyond Neptune by Voyager 1, and its companions orbiting the Sun are not alone in the universe. Research with Earth-orbiting instruments seeks evidence for life in the chemistry of any atmospheres around any of the objects circling their parent stars. Intense radiation across the entire electromagnetic spectrum from stars and galaxies can now be measured, expanding understanding of the physical origins of stellar colors and hues. Clever telescope designs and a dedicated spacecraft for detecting x-rays spectacularly opened this field and gained a Nobel Prize for Riccardo Giacconi (2002). The opportunities for science opened by the engineering achievements of access to space stimulated great imaginations. New astrophysical phenomena, many very energetic, have been discovered by telescopes exquisitely engineered to operate across the ultraviolet, x-ray, infrared, and gamma ray ranges. These phenomena include black holes, magnetars, x-ray and gamma ray bursters, neutron stars, x-ray pulsars—each as exotic in the universe as its name. Spitzer’s long ago vision came to life and flight as the Hubble Space Telescope. Launched in 1990 and four times serviced by the space shuttle, this huge engineering success has enhanced astronomical understanding of the cosmic structures and order displayed in Earth’s local galaxy and the vast universe beyond. And further knowledge is soon to follow thanks to the even more capable and engineering-innovative James Webb Space Telescope. Observational cosmology has flourished. The Cosmic Background Explorer (COBE) mission (1989–93) clearly confirmed the primary form and anisotropy of the background microwave radiation filling the universe. A Nobel Prize went to George Smoot and John Mather (2006) for this achievement. The Wilkinson and Planck satellites following COBE extended to higher order resolution of the background radiation spread across the measurable universe. Epilogue Sixty-plus years of access to space above Earth’s atmosphere have fostered discovery after discovery, revolutionizing concepts of the physical universe. The dramatic and exciting explorations have all been made possible by new engineering advances facilitating new science and by new science directions requiring new engineering technologies and implementation. The interplay and synergism of science and engineering continue, a brilliant collaboration greatly enabling humankind’s ongoing search for ever more depth in knowledge of its existence on the celestial rock known as planet Earth. About the Author:Louis J. Lanzerotti (NAE) is a retired distinguished member of the technical staff of Alcatel Lucent Bell Laboratories and is currently distinguished research professor in the Department of Physics at the New Jersey Institute of Technology.