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34

It is true. As soon as Rosetta hits the surface, its main systems will be turned off, including the attitude and control systems, as well as the main transmitter, the latter in order to meet regulations aimed at avoiding interference on deep space network communications channels. The software that will enable this ‘passivation’ will be uploaded ...


32

At first it might seem a bit crazy to crash a still working satellite into the comet. You could say that if you wait long enough the comet will come around again providing enough energy for more research. This does bring some risks however, to name 2 obvious ones, the satellite could slowly drift out of orbit or it could never wake up again due to the harsh ...


31

This was one of the questions just now during the Rosetta press briefing. This video was shown during the presentation: The triangular trajectory are hyperbolic orbits with respect to the comet and they'll (also, among other tasks also mentioned in the image you're attaching) serve to establish its mass. In essence ...


24

From ESA's FAQ page: Why was it necessary to keep Rosetta in hibernation for 31 months? To limit its consumption of power and fuel, and to minimise operating costs. During hibernation it was spinning once per minute and faced the Sun, so that its solar panels could receive as much sunlight as possible. Almost all of the electrical systems were switched off, ...


22

From the Rosetta wake-up FAQ (pdf): Q. Was Rosetta completely shut down? Almost. Only the computer and several heaters remained active. These have been automatically controlled to ensure that the entire satellite doesn't freeze as its orbit took it from 660 million km from the Sun out to 790 million km and back between 2011 and 2014. Everything else on ...


20

Philae can last many years (it's meant to survive perihelion pass, it has solar batteries, and it can withstand the long deep-space hibernation (it did it once already). Theoretically it could last as long as Opportunity on Mars. Unfortunately it doesn't have antennas to reach Earth - only Rosetta. It depends on Rosetta to forward data back to Earth. As long ...


19

The Wikipedia page for Philae suggest a 1-6 week mission duration. However, the design goal is always conservative. Consider the Mars rovers (Spirit and Opportunity) whose mission design goal was 92 days and Opportunity is at 3945 days now and going strong. They design longer, but ensure the minimum. So how long could it last? No one specifically knows,...


18

Orbiter The Solid State Mass Memory (SSMM) is 25 Gbit (about 3 GByte) with a 5Mbps data rate. The telemetry rate shall be switchable between 8 bps and 65536 bps and The bus throughput shall be minimal 131 kbps. The SSMM shall support an input data rate of up to 5 Mbps useable data (physical data rate excluding IEEE-1355 protocol overhead) The telecommand ...


16

There isn't any limit to how small bodies can orbit each other (gravity-wise) until you get to atomic scale where one of the remaining three fundamental forces (weak force, strong force and electromagnetism) take over and gravity becomes largely irrelevant. With smaller bodies, gravitational potential will only be that much smaller and required centrifugal ...


14

Let me just expand a bit on @Tildalwave's answer. Most landers on airless bodies need a propulsion system, because they will be going too fast otherwise to land. But that's only because most landings have been done on objects with a lot of gravitational mass. Let's just try and figure out what the escape velocity would be. Wikipedia gives us the following ...


14

What is an atomic force microscope (AFM) in the first place? An AFM uses a very sharp tip to "probe" around the surface of an object. As it gets closer to or further away from the surface, tiny changes in force are observed from van der Waals or similar "atomic" forces. A computer can stitch together a grid of individual passes over the ...


13

Rosetta is mainly tracked through radiometric means. They use 3 different methods: range, Doppler and ΔDOR. [2] Range measurements are conducted by sending a "ping" radio transmission to the spacecraft, which then responds with a "pong". The time it takes for the spacecraft to respond, that is the reaction time of the onboard electronics, is precisely ...


13

The spacecraft's own truss and elements are thermally conductive, so there's no need for hot air heat distribution. Air (or gas) is actually not such a good heat conductor due to its low density, unless it's highly compressed, at which point you risk mechanical damage to parts it would be heating up. It would also unnecessarily add mass to the spacecraft and ...


13

It did not travel in a straight line. It passed 4 planets for gravity assist1 in order to gain the velocity and change to the trajectory2 required to meet the comet. See Gravity Assist: Rosetta – Rosetta – first spacecraft to match orbit with a comet for details. The comet is currently approaching the Sun, but further from the Sun than Earth. So ...


12

Rosetta was spin-stabilized during her hibernation, which means that the solar panels were not optimally aligned to produce all required power for its transceiver, so in a nutshell - no. Part of this is explained in ESA's Rosetta Hibernation Wake Up FAQ (PDF): Q. How will ESA re-establish contact on 20 January? Will mission control send a signal? ...


12

The wake up is triggerred by the onboard timer in Rosetta. It is something like an alarm clock. When the timer triggers the start command, the system wakes up and runs a set of procedures. Here is an illustrative video which explains Rosetta's wake-up process. You can easily learn how the wake-up process works in the probe from this video.


10

Solar arrays are pretty much worthless beyond 4 AU or so from the Sun (depending on the size of the arrays of course). The Juno spacecraft will be the first mission to Jupiter (about 5 AU from the Sun) that uses solar arrays. In the case of Rosetta, it was easier to design the spacecraft to go to sleep for a while than it was to outfit it with solar arrays ...


9

Comet Chury moves at a speed of 37 km/s. If Rosetta were launched just in time for a rendezvous near Earth, it'd be traveling at maybe 12 km/s (relative to Earth) at a large angle relative to Chury. Let's just focus on Chury's speed for the moment and ignore the rest. Rosetta flies by Chury at an angle of let's say 90° and fires its harpoon. Now it has to ...


9

Remember that Philae was designed in the 1990's. MorphHex is at the edge of what technology of today can accomplish, it wasn't possible 20 years ago when Philae was designed. Most of all because adaptability would have to be done autonomously because of the 28 minutes time delay. The harpoons were supposed to fire once two legs had hit the ground. But it ...


9

Yes No (see update). From ESA's 15 November 2014 update on the Rosetta mission: Pioneering Philae completes main mission before hibernation 15 November 2014 Rosetta’s lander has completed its primary science mission after nearly 57 hours on Comet 67P/Churyumov–Gerasimenko. After being out of communication visibility with the lander since ...


8

Actually, Philae does have a propulsion system. As explained in this related question, its Active Descent System uses a cold-gas thruster to propel the lander towards the comet if needed.


8

Rosetta's approach and odd orbit (described well in the question and answer here: Is this really Rosetta's orbit around 67P?) are designed to gather the necessary information needed to achieve a safe orbit and eventually land Philae. The landing site is being selected now: "As many as five possible landing sites will be identified by late August, before ...


8

Adding to the existing answers: The triangular flight paths were needed to get enough images of the comet's surface, which are required for the low paths Rosetta flies today (and for dropping Philae close to the surface). Rosetta's orbit propagator is an innovation insofar as it uses landmarks on the comet (among other things) to find the comet's and its ...


8

While nothing is certain, even if there are no equipment failures it's unlikely that Philae would survive the comet becoming highly active as it approaches perihelion in fall 2015. EDIT: Seems I was wrong. Quote from Dr Ulamec, lander team manager: "Risk of the lander being blown off the surface by strong cometary jets is low - it has too high a density"


8

Indeed it's extremely difficult to accurately determine the mass of a comet without flying something past it at close range. Even if you assume an average density (which is not particularly safe, as little is yet known about the internal makeup of comets and how that varies from body to body), no earthbound telescopes (including Hubble) were able to resolve ...


8

Yes, the science/engineering teams will be able to use the radio communications between Rosetta and Philae to better pinpoint the location of the lander. However, by far the best data for finding the lander will be the CONSERT instrument, which has a part on the lander and a part on the orbiter. CONSERT works by transmitting radio signals from the orbiter to ...


8

Just speculating here, but Osiris in an Egyptian myth ascended a ladder into the heavens. So it makes sense to name a probe (or a component thereof) after an "astronaut" from Egyptian mythology. Why Osiris as opposed to a host of other potential namesakes? That probably comes down to what letters they had available to make an acronym with. There are project-...


7

Rosetta will shift between different hyperbolic trajectories. This means that it won't move in an ellipse around the comet, but escape it if not repeatedly powered to another hyperbolic trajectory in a series of flybys. Trajectory changes are planned every Wednesday and Sunday. It is not what most ordinary people would think of as an "orbit", hence ...


7

In fact there is a better name for 67P, which is 67P/Churyumov–Gerasimenko. It was named after the two people who helped discover it in 1969. Churyumov identified 67P while studying photographs of Comet 32P/Comas Solá, taken by Gerasimenko. FYI, the official comet naming convention can be found at the IAU website. They give the comet the name based on the ...


7

Agreed, orbiting can happen at pretty much any scale. To give an idea, 67P/Churyumov–Gerasimenko has an escape velocity of about 1 m/s. (removed reference to ISS experiment because that didn't rely on gravity) A quick experiment: for bodies that weigh 1 kg each and a radius of 1 m, the formula given by @Tildalwave yields an orbital speed on the order of $...


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