The First Europa Lander, What can be done first, cheapest & best? Options

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I think that many people in this forum would agree that somebody's going to have to land on Europa someday before the rather elaborate schemes to penetrate the outer ice layer will ever fly, if for no other reason than to get some relevant ground truth before committing to such an elaborate, expensive, and risky mission.

EO seems to have ruled out any surface science package for that mission (though it would be nice to change their minds! ), but I think that there is a valid requirement at some point to directly assess the surface properties of Europa in an inexpensive yet creative way. Some candidate instrument payloads might be:

1. A sonar transducer/receiver set embedded within a penetrometer to determine crust density and examine the uniformity of the ice layer within the operational radius of the instrument (looking for cracks and holes, in other words).

2. A conductivity sensor again embedded inside a penetrometer to measure the native salinity of the surrounding material and possibly derive some constraints on the composition of metallic salts in the European crust (saltiness has a major effect on ice properties, in addition to the obvious need to derive the salt content of any underlying ocean).

3. A seismometer for all sorts of reasons.


How does this sound? Any critiques, additions, or subtractions? I omitted a surface imager not only because of bandwidth/extra complexity considerations but also because it seems desirable to penetrate the crust in order to minimize as much as possible reading any contaminants from Io during surface measurements. The orbiter data could be used to sense and subtract this from the penetrometer readings.

[PhilHorzempa]

It seems that at the November 2005 COMPLEX meeting there were
4 options presented for a Europa Lander that could be included as part
of the Europa Explorer mission.

Each of these options assumes the same plan for initial descent.
First, the lander arrives, eventually, with the Orbiter in a circular 100-km orbit
around Europa.
Second, after separation, the lander fires a thruster to
decrease velocity by 22 m/sec. This puts the lander into a 100 x 1.5 km orbit
around Europa.
Third, a large rocket burn takes place at periapsis to decrease velocity by 1,500 m/sec.
This essentially stops the lander cold and it begins to free-fall the last
1.5 km to the surface. This is the Stop and Drop maneuver. The remainig descent
to Europa's surface is where the designs diverge.

These are details of each of the 4 proposed lander designs.

1. JMI - Jovian Moon Impactor - This probe falls all the way to the
surface, impacting it at 62 m/sec. It is designed to withstand 5,000 - 10,000 g's and
looks to heritage from the Deep Space 2 Mars penetrators. This is where a precursor
mission like DS-2 has its payoff.
JMI Mass = 65 Kg

2. EPF - Europa PathFinder - After the Stop and Drop, EPF free falls to the surface, but
cushions its landing with 3 airbags, similar in size to the Beagle 2 design. The EPF itself
is desinged to withstand 600 g's and is saucer-shaped.
EPF Mass = 220 Kg

3. ESSP - Europa Surface Science Package - After the Stop and Drop, the ESSP utilizes
thrusters to slow its descent. The thusters cut-off at about 10 meters and ESSP freefalls
to semi-soft landing at about 40 g's or somewhat greater.
ESSP Mass = 350 Kg

Each of these first 3 landers is designed to have payload masses of about 7 - 8 Kg,
a lifetime of 3 days, power levels of about 10 W,
with a total science data transmission of 200-300 MBits.


4. IML - Icy Moon Lander - A true soft lander, using thrusters all the way to the surface
after Stop and Drop. Landing at less than 40 g's and using an RTG.
TMI Mass = 825 KG
The TMI is designed to last for 30 days, to have a power level of 100 W, to have a payload
mass of 40 Kg, and to transmit a total of 7 Gbit of data.

I think that the IML and/or the ESSP may use crushable materials to cushion the
landing on Europa. Also, these landers are able to be considered since the new
mission design for the Europa Explorer envisions using the Delta 4 Heavy as the launch
vehicle and the use of a VEEGA trajectory. The VEEGA trajectory design utilizes 1 Venus
and 2 Earth flybys and enables 7,000 Kg to be sent on the way to Jupiter.
This contrasts with the original Europa Orbiter design that contemplated
a payload of only 1,500 Kg to Jupiter.




Another Phil