Previous atmospheresurface vehicles and their payloads

This part of the book provides a basic description, key data and a drawing for all planetary atmospheric or surface vehicles launched, or attempted, from the earliest examples to 2007. Key references concerning the design, payload and results of each craft or mission are given in each case so that the reader may find more detailed information elsewhere. For the payload experiments, the names in parentheses indicate the Principal Investigators (PIs) or otherwise-titled responsible experimenters. Details of the particular experiments and the results obtained (if any) can in most cases be found by searching publications authored (or co-authored) by those named.

The many vehicles are divided into six categories, reflecting the way in which they encounter an atmosphere or surface.

• Destructive impact probes (where the mission is intended to end with the vehicle being destroyed on impact with the surface). These probes are discussed only very briefly, since they are not landers yet do play a role in planetary surface exploration.

• Atmospheric entry probes (where the vehicle's design is driven by its mission in the atmosphere).

• Pod landers (where the vehicle is designed to land initially in any orientation).

• Legged landers (where the vehicle is provided with landing gear).

• Payload delivery penetrators (where the vehicle decelerates in the sub-surface to emplace a payload).

• Small-body surface missions (where the vehicle operates in a low surface gravity environment). These can include many operations that are possible in low gravity, and various types of surface element.

The diagrams in this part of the book were drawn using information gleaned from a variety of sources. While researching specific details for spacecraft, J. Garry and the authors were glad to receive help from the following people: Charles Sobeck, Bernard Bienstock, Corby Waste, Marty Tomasko, Marcie Smith, Dan Maas, Doug Lombardi, Satish Krishnan and Debra Lueb.

Finding accurate detailed information about the flight models of certain spacecraft has been difficult, not least because the hardware concerned is no longer available on Earth to view! In all of the diagrams, hardware items have been drawn only when they can be unambiguously identified in photographs or technical illustrations. Any errors are therefore of the authors' own making. Note that in some cases thermal blanketing has been omitted for clarity. The general style is that the lander or probe is shown in two side views (90° apart) in the upper left, its accommodation on the carrier in the upper right, and a larger, labelled perspective view in the lower part.

By way of a 'global overview', Figure II.1 shows a launch timeline of planetary landers and atmospheric entry probes. The first launches of such craft were, perhaps surprisingly, not to the Moon, but those of Venera 1 and its 'twin'; however, their inclusion here is somewhat marginal (see Section 16.1.1).

Japan:

Hayabusa/ MINERVA

Europe:

Huygens+ Beagle 2++Philae

US Other US Mars

-H+Rar

-H-tw-Sui ger 3 - 5

+Pioneer Ven +Viking Landers +-H-++Apollo 11 - 17 •veyor 1 - 7

Pathfinder MER

MPL/DS2 : Phoenix

+ + +

U in i l ll im r Tit + + +

i i

Mars/Phobos nera/VeGa i i i

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Launch date

Figure II.1. Launch timeline of landers and atmospheric probes. Included are all launches, or launch attempts to 2007, carrying one or more craft able to operate on the surface of another world or in its atmosphere. NEAR-Shoemaker is included despite not having been designed to operate on the surface of an asteroid. Excluded are destructive impact probes and the tests of the Apollo LM and Soviet LK performed in Earth orbit.

Table II.1. Successes and failures of launch attempts of planetary landers and entry probes, in terms of the goals of the landers and entry probes at their destination. Some missions that failed during cruise, i.e. before the lander or probe was deployed, still produced useful data (e.g. Phobos 2, lost in Mars orbit). Some useful descent data were returned by landers that failed during EDL (e.g. Mars 6), and the atmospheric probes Venera 4, 5, 6 were all successful despite not reaching the surface

Outcome Number of launches

Launch failure (all of which were Soviet Luna

8

attempts in the period 1963-1975)

Failed to leave Earth orbit (all of which were

13

Soviet/Russian lunar, Venus or Mars missions)

Failed during cruise (often for propulsion, thermal

13

or electrical reasons)

Lost during, or very soon after, entry, descent or landing

13

Currently en route (Philae)

1

Not launched yet (Phoenix)

1

Success

40

Total

89

Particularly evident are the evolving programmes of the 'space race' era, with many launches to the Moon by the USA and Soviet Union, beginning with Rangers 3-5 in 1962 and ending in 1976 with Luna 24. The large number of launches in part reflects the high failure rate, in terms of launch failures, spacecraft failing to leave Earth orbit, failures during cruise, and crashlandings. Table II. 1 presents a breakdown of the successes and failures. The Soviet Union took advantage of all bar four of the Venus launch windows from 1961 to 1984 (the 1983 window being used to launch orbiters instead), as illustrated by the clear periodicity of the launch dates. Many Venus and Mars projects have involved separate launches of multiple (usually two) spacecraft, in part to provide redundancy against failure and the long wait until a reflight can be attempted at the next launch window. For the Venera missions this proved to be a good approach, since one craft, but not both, were lost in each of the 1967, 1970 and 1972 windows. Twin missions are also able to yield complementary data, and the ground segment costs are less than they would be if the missions were not under way near-simultaneously. For the Moon, launch windows are frequent enough for the twin flight approach not to be necessary, while in other cases only a single craft has been launched, either for budgetary reasons or because redundancy is implemented by other means.

In parallel with (and in many cases as part of) these launches of landers and atmospheric probes, there have of course been equally vigorous programmes of flyby and orbiter missions. In many cases the lander or probe is delivered by a craft that carries a scientific payload of its own, for operation during cruise, flyby or in orbit around the target world. Quite often they also play a vital role as data relays for the lander or probe.

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