Reading Passage 2
The Pioneer Anomaly
A It’s been more than four decades of incessant theorising and perplexed head-scratching for scientists, engineers and astronomy fans across the globe, but thanks to a recent study published in the journal Physical Review Letters, we finally have some answers to what has been causing the deceleration of NASA’s Pioneer 10 and 11 spacecraft – otherwise known as the “Pioneer Anomaly”.
B Pioneer 10 and 11 were launched in 1972 and 1973 respectively, and were the first spacecraft to travel beyond the solar system’s main asteroid belt. Their claim to fame, however, changed the moment they skirted past Jupiter and began their journey towards Saturn, as it was at that point – by then already the early 1980s that scientists and navigators discovered something had gone terribly awry: the two spacecraft seemed to be slowing down.
C As Bruce Betts of The Planetary Society explains, the scientists involved in the project had anticipated most of the slowing down due to “the gravitational pull of the Sun and other massive objects in the solar system”. In fact, when the deceleration was first observed, it was so small that it was dismissed as an insignificant, temporary phenomenon, and attributed to the effect of dribbles of leftover propellant still in the fuel lines after controllers had cut off the propellant. It would take until 1998 for a group of scientists led by John Anderson of Jet Propulsion Laboratory (JPL) to confirm that, even at 13 kilometres from the sun, the two Pioneer spacecraft were still losing speed at a rate of approximately 300 inches per day squared (0.9 nanometres per second squared). The first theories of what might be the cause followed soon thereafter.
D The late 1990s were an important time for the field of astrophysics, with the Hubble Space Telescope observations of distant supernovae having only in 1998 confirmed that the universe is expanding at an accelerating rate. Anderson et al’s confirmation of the Pioneer Anomaly the same year seemed to offer a demonstration of the very same phenomenon of expansion within our own solar system – a theory that plenty of scientists quickly embraced. Others yet ascribed the deceleration to dark matter, while some suggested the spacecraft, as Toth and Turyshev put it, might’ve “unearthed the first evidence of extra dimensions”. The possibility that a new law of physics directly contradicting Einstein’s general theory of relativity might be to blame was also considered.
E In 2004, Turyshev decided to get to the bottom of the Pioneer anomaly. Since the two spacecraft had stopped communicating with earth (Pioneer 11 first in 1995, and Pioneer 10 less than a decade later in 2003), all he could depend on were old communications and data; so, with the monetary aid of the Planetary Society and its eager, dedicated members, he began to gather the data from a number of different sources. There were two types of data that he needed to procure for his research: the “housekeeping data” engineers had used in order to monitor spacecraft operation, and Doppler data.
F The data came in all sorts of forms: some were in digitised files offered by JPL navigators (a lucky find, as punch cards were still the preferred method of data storage back in the 1970s), while others were in magnetic tapes accidentally discovered under a staircase in JPL. All in all, there were more than 43 gigabytes of data – an admirable result, considering that at the time the two Pioneer spacecraft were launched there had been no formal requirement that NASA archive any of the records collected, and it had only been due to sheer luck and a former Pioneer team member’s diligence that any telemetry data had been saved at all.
G Once all the data had been collected, the formidable task of going through the volumes of information began. It was neither quick nor easy, and it required the assistance of a variety of people, including JPL engineers and retired TRW engineers who had worked on the Pioneer project, who had to consult with each other in order to interpret old blueprints and reconstruct the probes’ 3D structure. In the end, however, the team’s perseverance paid off, and Turyshev’s suspicions which had initiated the study – were confirmed: it was the electrical subsystems and the decay of plutonium in the Pioneer power sources that were to blame for the spacecraft’s bizarre trajectory – more specifically the heat they emitted. This was corroborated by the discovery that other spacecraft with different designs had not been affected in the way Pioneer 10 and 11 had. As Turyshev said, speaking of the study, “the story is finding its conclusion because it turns out that standard physics prevail. While of course it would’ve been exciting to discover a new kind of physics, we did solve a mystery.”
Questions 14-20
The reading passage has seven sections, A-G. Which section contains the following information?
14 The contemporary context of John Anderson’s study
15 How Turyshev’s study was conducted
16 A description of the journey of the Pioneer aircraft
17 How data was normally cached at the time of the Pioneer launch
18 Why Turyshev’s study couldn’t rely on new information
19 The name of a scientific publication
20 The original theories for the Pioneer anomaly
Questions 21-25
Complete each sentence with the correct ending A-H below.
A played a pivotal role in Turyshev’s study.
B coincided with another scientific breakthrough in its field.
C leftover propellant had been expected to cause issues.
D contradicted contemporary theories about the Pioneer spacecraft.
E ceased communication later than its predecessor.
F was inspected by former TRW engineers to confirm its authenticity.
G exceeded all expectations in terms of quantity.
H external factors had been taken into account in the planning stage.
21 NASA’s Pioneer 10 spacecraft
22 The Planetary Society
23 Some of the spacecraft’s deceleration was not a surprise because
24 John Anderson’s study
25 The data Turyshev used in his study
Questions 26-28
Choose THREE letters A-H.
Which THREE of the following statements are true of Turyshev’s study?
A Former Pioneer team members were recruited to help to understand the data.
B It was an initiative by the Planetary Society that instigated it.
C It provided us with the first proof of extra dimensions.
D It identified head build-up caused by the Pioneer design as the culprit behind the anomaly.
E Parts of the Pioneer spacecraft were recreated to help with the study.
F The analysis stage of the study was particularly time-consuming.
G It proved that spacecraft with design similar to the Pioneer 10 and 11 faced similar issues.
H Turyshev was unhappy with the result of his investigation.
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