Book review: Haynes Cassini-Huygens Owners’ Workshop Manual

An in-depth look at the technology behind the mission that’s been delivering information from space for a decade.

Spacecraft engineering is a challenge second to none, partly because of the radiation and thermal environment of space, but also because, once launched, a spacecraft is physically inaccessible and thus difficult to mend if it goes wrong - especially true if it’s on a seven-year journey to Saturn.

This latest incarnation of the Haynes workshop manual is dedicated to one such spacecraft: the Cassini Saturn orbiter and its sister ship the Huygens Titan probe.

The Cassini-Huygens Owners’ Workshop Manual (£22.99, ISBN 9781785211119) has been compiled by Ralph Lorenz, a planetary scientist and aerospace engineer who worked on both elements of the Cassini-Huygens project in three countries for over 25 years. His wish to “remain faithful to the ethos of the original Haynes Manuals for car repair” is borne out by the level of technical detail in the book. Although much information would, he says, be “tedious, proprietary and/or subject to US export control,” he aims to “hint at the nested levels of artful design, meticulous craftsmanship and diligent operation that pervade the project”.

He succeeds, in a couple of hundred pages, by describing the dual spacecraft platforms and payload instruments to a level of detail probably not seen outside project documentation. Each section, from mission origins to ongoing science activities, is copiously illustrated with colour photos and diagrams and black-and-white line drawings. The book is further enhanced by three pages of abbreviations and a useful index.

Although Cassini-Huygens was launched in 1997, and the Huygens probe parachuted its way to Titan’s surface in 2005, the book is timely in celebrating the final phase of the mission as the Cassini orbiter begins its descent into Saturn’s atmosphere. Having returned data for more than a decade, it is time to end the mission and dispose of the orbiter according to planetary protection guidelines (thus eliminating the possibility of collision with a moon that may harbour life). As the author puts it, “once the plumes of Enceladus revealed the existence of a near-subsurface liquid water reservoir”, the planetary protection stakes were raised in the Saturnian system.

As much as it celebrates the mission, the coverage is pragmatic and includes many of the problems faced. Sometimes instruments worked perfectly, explains the author, but data were lost “when the solid state recorder was incorrectly set” or the deep space network was “unable to receive data that could only be transmitted once”.

At other times, “observations were degraded by the sheer sensitivity of the instrumentation”, for example a “faint banding” on images derived from a beat-frequency clash with the pixel read-out clock. The latter wasn’t seen in tests on Earth because of the noisy electrical environment of air-conditioners, computers and mains power; it took the radio silence of Saturnian orbit to reveal the true sensitivity of the instruments!

After 60 years of the Space Age, we either take planetary exploration for granted or simply ignore it. Reading this book will not only rekindle an appreciation for the artifice of engineering in challenging environments, but should also cure any ambivalence towards this fascinating application of engineering techniques.

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