“Well, he only had a minute,” she said, “and he will talk to you tomorrow, and he didn’t think I should tell you until he was sure, tomorrow. But I think this is something you should know about, and pretty soon. So will you not tell your Dad I told you?”
I nodded solemnly and leaned closer to her.
“Well,” she said, “it looks like your Dad, and probably me, are going to get another mission. He was at a big meeting of the University Space Research Associates, who are the people who have a special experiment they want him to do for them, and if NASA agrees then your dad will go up to the ISS to do that. That means you’ll probably have to go stay with Sig and your mother in D.C., at least for a while, because they’re moving there real soon. And if your Dad goes, it’s a three-month mission, so with training time and everything he won’t be back till school’s out.”
“Will you be back sooner?”
“Unh-hunh. Probably I’ll just be at training for a while, about as long as your dad, and then I’ll come back ten days or so after we fly. When I get back I’ll come and visit you in Washington, if you want me to.”
“Sure.” I was holding onto her hard, but she didn’t try to make me release my grip. “It’ll be great if you can come and see me.”
Like I said, Christmas that year was almost okay.
* * * *
The funny thing is the longer I spend going over the family records, getting things in order for Clio, the more confusing some things get. There was the Chris Terence who I knew as “Dad,” and he was kind of inconsistent, moody and a little scatterbrained; there was the Chris Terence who was Mom’s first husband, brilliant and fascinating but arrogant and sometimes a plain old jerk; there was the Chris Terence of the nightly news and of dozens of academic conferences, a powerful, clear, articulate voice for space science; and there was the Chris Terence of the NASA records, which I finally got on the fiftieth anniversary of his death—an efficient, dedicated, highly regarded astronaut whom other astronauts liked to work with. But for what it was like to be him . . . well, that’s one of those questions sons never know about fathers.
He had been active for a long time in the University Space Research Associates. It was an outgrowth of half a dozen older projects and cooperative organizations, and he’d been part of those, too. Everyone knew that if there was ever going to be a voice for pure science in the space program, it would have to come from the university research community. The idea was simply that the various large college departments of space science, astronautics, astronautical engineering, planetary science, and astronomy—where so much of the real basic research into space-related subjects was done—should get together in a consortium, pooling part of their funds, raising some for the consortium itself directly, and come up with a long-term program of pure scientific research which they could do cooperatively with NASA, ESA, and any other space agency that would let them. One of the first fruits of this was the Far Side Radio Telescope (FSRT), the experiment that Dad would be working with up at ISS.
The basic idea of the FSRT was simple. What we can know of objects out in space is what comes to us as electromagnetic radiation: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and cosmic rays. Several of these had really only become available for study once there were platforms in space—ultraviolet and infrared don’t penetrate the atmosphere well, and X-rays and cosmic rays scatter so much in the atmosphere that it’s all but impossible to tell, from a ground-based station, where they came from. Thus it was not until orbiting satellites were able to get above Earth’s atmosphere that we even began to have any idea where most of these kinds of radiation came from, or how much any given object in the sky was putting out.
Visible light, of course, had been one of the basic tools for studying the cosmos since people first looked up into the night sky, more so since the invention of the telescope in the seventeenth century. But here, too, space had made a major improvement, because air blurred the light coming in (the same phenomenon that made stars twinkle) and dimmed it as well; hence, with a mirror only a fraction the size of the large telescope mirrors on Earth, the Hubble Telescope had been able to see very far, deep, and accurately into the universe.
At first glance, since radio waves are relatively unaffected by passage through ordinary air, it might seem that radio astronomy would suffer far fewer problems from the Earth’s blanket of air, and thus radio astronomers would benefit far less from space exploration than any other kind of astronomer. So far that had been true, but the Interuniversity Group was out to change that, in their first big project together.
The problem was not that the air blocked, scattered, or distorted radio waves; it did those things only to a minor extent. The problem was that about the time that radio astronomy was developing in the 1920s—as scientists came to realize that the hiss and crackle of “static,” which could be heard over any radio, partly originated from sources not on this planet—the world had begun to fill up with radio broadcasting stations. (It was natural enough; radio had to be invented before anyone would know about radio telescopes, but once radio was invented there were bound to be stations on the air.) The Heaviside layer in the upper atmosphere bounced radio waves around the world; if an astronomer wanted to listen for a given frequency from some star, no matter how carefully he might point his antenna at that star and no other, the more sensitive his detector, the more likely he was to get a college station from Fargo or the farm report from Chile. Further, the Earth’s atmosphere is alive with electrical storms, and our strong magnetic field creates vivid auroras at the poles, and both of these are also powerful sources of radio waves, creating vast amounts of noise through which the astronomer must try to hear the faint signals from beyond. In fact, coming in only behind the Sun (a blazing nuclear fusion reactor) and mighty Jupiter (with the solar system’s most intense magnetic field), the Earth is the third largest source of radio noise in the solar system.
Merely to have put a radio telescope in orbit would not have done much good. It not only would remain close to the noisy Earth, but it would be in a straight line from many of the noise sources; the only advantage was that since it would be far above the Heaviside layer, fewer stray signals might scatter into its directional antenna. Thus there had been relatively little work with radio telescopy above the atmosphere, because the advantage to be gained was slight compared with what could be gained in most of the rest of the electromagnetic spectrum.
However, better launch vehicles and tools had come along, and now there was a new possibility, one that the Interuniversity Group wanted to exploit. The Moon, with only a very weak magnetic field, does not put out much radio, and one side of the moon is forever turned away from the Earth. Furthermore, 50 percent of the time the side that is turned away from the Earth also faces away from the Sun. And finally, because Jupiter goes around the Sun in about twelve years, matters worked out so that 5/12ths of that 50 percent—or 5/24ths in all, just over a fifth—of the time, the Moon would also shield a radio telescope on its far side from Jupiter.
At such times, with almost all the noise of the solar system screened out, a very delicate detector could be used. It meant a real possibility of seeing deeper into the universe in the radio spectrum than we had ever done before, and of getting back results with far greater certainty.
There was no way of simply constructing a radio telescope on the Moon as we would do on the Earth, however. Earthbound radio telescopes are gigantic dishes, like radar dishes or television satellite antennas, but much larger. The ones that are small enough to move, move on gigantic pieces of machinery; crews of dozens staff them. To build something on that scale on the Moon—let alone on the back side—was far beyond our capabilities in 2006, and we weren’t about to try.
Rather, we took advantage of some naturally occurring phenomena. The Moon has plenty of craters of all sizes, even on the far side (though the very largest, for unknown reasons, are concentrated on the near side). The craters themselves are far
from being perfectly parabolic, as an ideal radio dish would be, but they are certainly large and they make adequate reflectors. If they could be corrected to reflect waves from a particular point toward a central antenna, the radio telescope could even be aimed with a fair degree of precision. The natural lunar soil offered some radio reflectivity; a point fifty meters or so above the bottom of a half-kilometer-wide crater should have a fairly strong signal.
The Far Side Radio Telescope was an ultrasensitive radio receiver with enough computer memory to store a very accurate digitized recording of whatever signal it received. It was to be mounted atop a small robot lander, which would fly to a preselected crater on the far side, land near its center, and then put up an antenna, a thin piece of aluminum pipe. Three small robot carts would depart automatically from the lander, crawling out about 100 meters from the landing site, at 120 degrees from each other; each would be dragging several long wires attached at various points to the antenna. When the carts were in position, a small tank of helium would be used to pressurize the inside of the telescoping antenna, causing it to extend upward very slowly; in radio communication with each other, the guy wire robots would continually adjust line tensions to keep the slender aluminum rod perfectly vertical. As the helium pressed each section into its final place, a snap lock would keep it there. At last, after a couple of hours, the aluminum pipe would reach fifty meters into the empty sky of the far side of the Moon, vertical and well-guyed, somewhere near where the crater would reflect radio waves. The computer on the FSRT would work out what were the “quiet times” when Earth, Jupiter, and Sun were all out of line-of-sight from the radio; two thousand kilometers of lunar rock would block and attenuate the radio signals from those strong noise sources—and the FSRT would be able to hear and record fainter signals, from more distant places, more accurately than any instrument ever before.
Two additional features were needed to make it work. The first of these was the most urgent. Unfortunately, a robotic research station that is placed in an area where radio waves from Earth cannot penetrate also cannot receive orders telling it what to look at, nor can it send data back. A relay station was needed, and because the relay station itself was potentially a source of noise, it needed to be a very quiet one.
The solution was the “halo satellite,” which took advantage of an odd phenomenon in orbital mechanics, one of those cases where the mathematics of physical equations predicted something that then turned out to be true in the real world. Prior to computers, most many-body problems in orbital mechanics—that is, problems that involved more than two bodies attracting each other gravitationally—were not soluble by any means available; the solutions had to be approximated by treating them as a set of separate two-body problems.
Around the turn of the nineteenth century, Lagrange had pointed out that there were a few places in orbit around a two-body system (like the Earth and the Moon, Mars and Phobos, or the Sun and Jupiter—any system where you could ignore the other bodies temporarily) that did have solutions, stable places that would behave very much as if there were an attracting body there, even though they were just empty space. In those five spots, called “Libration points” because they were places where the gravity and motion of the system balanced, a satellite could stay indefinitely, with no need for fuel or energy to “station keep”—i.e., to maintain its position.
Those places were a midpoint where gravity balanced between the two bodies so that neither of them ever tugged the satellite one way or another; two places in line with the two bodies but on the outside, so that the satellite orbited the combined center of mass of both bodies with exactly the same period with which the two went around each other; and the places which formed an equilateral triangle with the two bodies, one ahead and the other behind the smaller body in orbit, where any motion toward one body would result in a stronger attraction by the other and pull the satellite back into place.
Thus the Earth-Moon system (and any other case of one body orbiting around another) has five “Lagrange libration points”: places where a spacecraft can sit without expending fuel to keep itself in a constant relationship with the Earth and Moon. These are almost always referred to by L plus a digit. L1, L2, and L3 all lie in a line with the Moon and the Earth; L1 between them, L2 beyond the Moon, and L3 on the opposite side of the Earth from the Moon. L4 is 60 degrees ahead of the Moon in orbit; L5 is 60 degrees behind. The Lagrange libration points had been of great interest since the late 1960s, because they are the most energy-efficient places to put a space station, and when it cost $100,000 to move a pound of fuel into orbit, energy savings were vital.
The Lagrange points have another odd feature. Because they are attractors (things near them tend to fall toward them), it is possible for a satellite to orbit them, even though they are just points in empty space.
This was the birth of the idea of the halo satellite. A satellite orbiting L2, in about a two-week orbit, will always have both the entire far side of the Moon, and the facing side of the Earth, in direct line of sight. It was called a halo satellite because from the Earth it appeared to be making a circle around the orb of the Moon—and thus was never out of sight of either the Earth or the far side. The relay transceiver on the halo satellite, in turn, could be turned entirely off whenever the FSRT was working, so that the only thing running on board was a small clock set to turn the halo satellite back on at a pre-arranged time, then receive data from the FSRT and relay it back to Earth during the “noisy” periods. For technical reasons a pair of halo satellites worked slightly better, giving more complete coverage of the Moon’s back side. No one made much of a point of it, but a halo satellite in place would also mean that if humans ever ventured to the far side of the Moon, they would be able to radio home—a drastic improvement from the days of Apollo.
The other device was a simple, incremental improvement that would allow the FSRT to become a steadily better tool for decades to come. Weighing just forty pounds, the Self-Propelled Ultralight Microantenna (SPUM) was designed to be launched to the Moon using any convenient system; it would find the FSRT by radio beacon during a noisy time and descend into the crater, avoiding the guy wire robots and the previously arrived SPUMs by receiving information from the FSRT computer. Once down, it would unfold a simple wire-frame antenna, not much different from an old-fashioned umbrella, about fifteen meters across—an easy enough size to handle in the light lunar gravity.
Coordinated by the FSRT, the SPUM would run a series of test radio beeps so that the FSRT would know its exact location, plus how to translate what the SPUM said about its position into the FSRT’s more general coordinate system. Each added SPUM would increase both the signal strength and the ability of the FSRT to focus; a few hundred of them would make the FSRT into an extraordinarily powerful and effective instrument.
The FSRT, halo satellite, and SPUMs were all to be powered by batteries recharged by solar cells. Since by definition when there was sunlight it was a noisy period, the charging process should create little interference with the work of the FSRT.
The system was elegant and cheap; it took advantage of enormous improvements in computers to minimize expensive mass being sent to such a difficult location.
But everyone had learned the bitter lesson of the Hubble Telescope, which had originally gone up with a warped mirror, unable to focus properly. Though it had been successfully repaired, the damage it had done to NASA’s public image had been incalculable. The University Space Research Associates, with a far smaller budget and much less public visibility than NASA, needed this first bold mission to be a complete success, and so they had determined that they would thoroughly test each component before sending it on its way. In late 2005, the halo satellite had checked out perfectly, and a Centurion/Starbooster combination had carried it into halo orbit, from which it was reporting that results thus far were perfect.
Next would come testing the FSRT’s receiver in Earth orbit, to make sure that it would work properly in vacuum and in the
alternating tremendous heat and cold of sunshine and shadow in space. Chris had been assigned to do the full checkout of the FSRT at the ISS, following which, if time permitted, he could use extra time on the ISS for astronomical observations for his own projects and assist the rest of the crew with assignments coming up from the ground.
This was the seventh American flight of an Apollo II on top of a Centurion/Starbooster combination, the temporary configuration to augment the three remaining shuttles until Starbird would replace them later in the decade.
Lori Kirsten was to be the pilot for the mission that would take them up; she had trained with the astro-Fs in France and knew Apollo IIs thoroughly, but she hadn’t actually flown one before. The mission’s principal functions were Chris’s FSRT mission, and getting another escape module (and better still, one that was neither Russian nor French) up to the ISS.
It was really a good thing that Chris and Lori were the only crew; the FSRT took up a great deal of room in the Apollo II so the other four crew seats had been removed.
“Ever feel like a museum reenactment?” Chris muttered to Lori as they strapped in for launch.
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