58

The Arecibo raqdio telescope has a $300\ \mathrm m$ diameter mirror. Let's consider a radio wavelength of $3\ \mathrm{cm}$ ($10\ \mathrm{GHz}$) for convenience of arithmetic. That gives a diffraction limited beam width of $100\ \mathrm{µrad}$, so at 100 light years, the signal would be spread over an area $10^{14}\ \mathrm m$ across. The Arecibo signal was ...


56

Tardigrades can survive vacuum, low temperatures, and moderate radiation for quite a while. They're multicelled organisms. How tough is the toughest hypothetically viable single-celled extremophile? How sure are you that we've found all of them on Earth already? It's a matter of caution. Contamination of another planet (or moon) is likely to be irreversible,...


49

I wrote the article you are referencing. @Hobbes has it exactly correct. It is a lightweight vehicle that can launch on even a small rocket, and takes advantage of gravity assists and favorable celestial mechanics to catch Triton at just the right time for encounter with the plumes illuminated. It will image the entirety of Triton in sunlight on approach, ...


43

ERT is Earth Received Time. I.e., when we find out about the event. source


33

@SteveLinton's answer is excellent and I'll just confirm below that its logic and numbers are correct. Then I'll show that you can do it optically as well, but with 10 meter telescopes instead of Arecibos you run into a challenge because each individual light photon carries most of the total received power per second. Radio From this answer: One ...


25

So back in the summer of 1935, some folks down in Australia were having problems with a beetle's larvae that were nomming on the sugar cane roots and harming crops. Since traditional methods of getting rid of the pest failed, they decided a good approach would be to introduce a few cane toads to go eat the beetles... a hundred or so of them in a couple of ...


25

The journey to the destination is about always completely pre-planned. All the gravity assists, close fly-bys, and so on, are planned before launch - and often long before the probe design is completed, as often the requirements of the trajectory influence design considerations: ability to hibernate, delta-V of the engines, tolerance to heat if the probe is ...


24

First order analysis Given that we have practical ion thrusters, it's time to look at them. Deep Space 1 The DS1 probe massed 387kg, had 83kg of fuel, operated for 162 days, and generated 92mN. So, it generated about 0.2mm/s^2. The craft is not tanks-dry, either. It has approximately 6 months (180 days) of fuel per design. That's a roughly 20% fuel ...


22

Sometimes you don't want to hibernate the craft, because it has scientific operations to perform during the interplanetary transfer phases. But even when you don't: Deep space hibernation is risky. There is always the risk that the wake-up procedure - whether triggered by the vessel or by the ground station - won't work and the vessel will not recover. It ...


21

If you only count planets, then I believe it's MESSENGER at six. Though your question was explicitly: "Which probe that we have launched has received the most gravitational assists?" The winner there is Cassini, hands down. It is on Titan flyby number 93 125, so far. And it's flown by other moons of Saturn. Plus the four planetary flybys on the way to ...


21

The Voyagers have been so reliable due to careful design, plus lots of redundancy. Voyager employs three dual-redundant computer systems per spacecraft. The first, the CCS, is nearly identical to that flown on Viking, performing sequencing and spacecraft health functions along with new ones necessitated by the addition of the other computers. Telemetry ...


20

Power and Mass From this paper (emphasis mine): The specific power of an 241Am-fuelled RTG cannot match that of a 238Pu system (except perhaps at small power output levels); however, the design work undertaken provides confidence in potential capability and performance of 241Am systems for future space missions. Medium-sized RTGs in the 10 W to ...


19

The problem with using nuclear fission reactors as means of power to propel spacecraft is twofold: our own aversion to anything nuclear due to environmental hazards and the problem of reaction mass still persisting, regardless of your energy source longevity and power density per its own mass. Let's explain these points a bit more. The reaction mass problem ...


16

Considering that Voyager 1 is already 126 AU from the Sun 36 years since launch, there should be no reason that it would not be possible energetically using a normal launch, small maneuvers, and planetary flybys. Just a Jupiter flyby should be sufficient. Jupiter will also provide the necessary change in inclination. Designing a probe that is assured to ...


16

Any object in space has several sensor signatures: Reflected optical - light reflected from surfaces. If you illuminate Voyager, its glint will be detectable. Emitted optical - light emitted by bulbs aboard. For energy conservation reasons there are none. If there is an insanely sensitive optical sensor exactly on the line between a star and Voyager, ...


16

This is referred to as 'kick stage' motor and is commonly used. One example being Star 37. A larger Star 48 is what sent New Horizons on the way to Pluto


15

Currently functional and proven technology is limited to basically no interstellar travel at all. To reach one of our stellar neighbors (like Proxima Centauri), one of the fastest space probes we have now, New Horizons, would take 54000 years. There are multiple proposed methods of sending spacecraft interstellar distances (in shorter time spans) such as: ...


14

DSN time is competitive, and not cheap. So, besides the costs that Tom mentioned in getting the camera there (and an appropriate relay satellite), you have to consider the costs of getting the data back to the earth. For the space station, it's only ~370km (230 miles) up ... relatively close, and they can use much smaller dishes than what's required to get ...


14

You can calculate this using the diffraction limit: $$\sin\theta\approx{\lambda\over D}$$ Where $\lambda$ is the wavelength being used for the radio communication, $D$ is the diameter of the dish (either on the spacecraft or on the ground), and $\theta$ is the beam width. You need to point the antenna accurately enough to keep the target in the beam. The ...


14

The only spacecraft that I'm aware of that were fully sterilized were the Viking 1 and Viking 2 landers. They went through dry heat microbial reduction. That page notes that some parts of the Beagle 2 lander were sterilized. The MSL (Curiosity) drill bits and other components were sterilized, though the drill bits were later exposed to a clean-room ...


14

OK let's first understand units. The decibel (dB) is a base-10 log scale without units and dBm is a similar decibel scale for power referenced to 1 milliwatt. They also include a factor of 10, so for example 10 dB is a ratio of 10^1, 20 dB is a ratio of 10^2, etc, while 10 and 20 dBm would be 10 mW and 100 mW. But in the block quote, they use dBW instead of ...


14

The latest measurements used by JPL Horizons to calculate its trajectory were reported on 3/27 as follows: 2018-Mar-27: Two reporting sites (J94 & K93) extend data arc one month. That is the last update that is included on the site, and thus seems likely to be the last update. Looking at the two mentioned observatories, neither of them has a public ...


14

It's a fast flyby in the $500M cost class (a Discovery mission). So not really comparable to Beresheet. A rare, low Δv trajectory (Fig. 1) enables an MMRTG-powered spacecraft fitting under the Discovery cost cap. The mission would have to be launched in 2026, for a Neptune encounter in 2038. New Horizons has effectively demonstrated the scientific ...


13

Voyager 1: separated from Centaur stage with velocity 18.3 km/s (relative to Earth, Dave Doody, Deep Space Craft: An Overview of Interplanetary Flight, 2010, page 120). Then 76.5N Injection Propulsion Unit of V1 did burn its solid fuel in 43 seconds giving additional 1,7 km/s (?), injecting the spacecraft into Hohmann transfer orbit. IPU was separated, and ...


13

I'm not up to a complete exhaustive survey of every possible contestant, so I've focused on relatively recent orbiters. I found a few that beat Cassini. The figures I've found so far are occasionally a bit contradictory or squirrelly -- masses are rounded differently here and there, some sources give the design tankage while others give the actual flown ...


12

The software used for this at JPL is all homegrown. A great deal of effort goes into the optimization algorithms for complex, multi-body and/or low-thrust trajectories. You can try to request tools here. Examples are CATO, Mystic, and MALTO. However these tools are not really intended to be "user friendly", and require a great deal of domain expertise to ...


12

The closest to this design was the Ulysses probe, which ended up in a heliocentric orbit with a semi-major axis of 3.37 AU and an eccentricity of 0.603, and an orbital period of 6.2 years. (Orbital elements available here.) It was launched in 1990, and operated until about 2008. However, the point of this probe wasn't to take pictures from deep space, but ...


12

Unlike chemical rockets such as hydrazine (a monopropellant, which doesn't require separate oxidizer and fuel to burn), water is just the reaction mass — not the energy source. The Comet-1 thruster that the DSi Prospector series is using is electrothermal, so it requires a substantial electrical power supply in order to energize the water (presumably ...


12

A Falcon Heavy on the launch pad masses about 1400 tons. Its payload to low orbit is about 64 tons (fully expendable) (both figures from wikipedia). So it would take, not 2, but about 22 Falcon Heavy's somehow strapped together to lift one fully fuelled one into orbit.


11

It really depends on the gain of the antenna used. In antenna design you can either go for gain (directing all the energy into a narrow cone) or wide response (sensitivity in all directions). The further away the space craft you want to communicate with, the more important gain becomes. The gain of an antenna is "almost free" - up to a limit it does not add ...


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