Comments by "H. de Jong" (@h.dejong2531) on "James Webb Space Telescope Update and a New Mystery" video.

  1. as it turns out, this is really hard. The only way we know of to create a gravitational force is by having lots of mass. You'd need an entire planet's worth of mass to create a zero gravity chamber here on Earth. Launching into orbit is a lot cheaper.
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  2. JWST is not large enough to provide detailed images of exoplanets. We'll see them as a single point of light. This video shows Hubble's images of Pluto: https://www.youtube.com/watch?v=Tu327ZWGG1M
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  3. That's not how science works though. Science starts with observations. Then scientists try to find an explanation for those observations, this becomes a model. The model is tested using more observations or experiments. When the model holds up and makes accurate predictions, it becomes a theory. The word 'theory' has a specific meaning here: it's not the colloquial opposite of 'practice'; a scientific theory is a model that has been shown to be accurate in a wide range of circumstances, and the best way we currently have to explain how things work. Models and theories are always subject to improvement.  You are assuming scientists make assumptions. They don't: observations are always the starting point. When an astronomer presents his findings about stars being 'constant and stable', he'll say 'based on [large number] of observations of [another large number] of stars, I found that 73% of them have no observable variability, and the variability in the remaining stars was [table summarizing findings]". Less knowledgeable people then paraphrase this as 'stars are constant and stable', but that's not what the outcome of the study was.  Science does not and should not stop at observations. Models are what makes science worthwhile, because with a model, we can start to do real work. Gravity is a model that allows us to calculate the orbit of a satellite, etc.  The variability of stars is well-known in astronomy. Variable stars have long been a focus of astronomical study, because it turns out there are variable stars that have a predictable variability, which can be used to measure distances.
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  4. It can't get back to Earth orbit - it doesn't have thrusters on the side facing away from the Sun. They'd have to rotate the spacecraft to point a thruster that way, and this would expose the mirror and instruments to direct sunlight.
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  5. 5 years is the length of the primary mission. That's how much time they need to answer the questions this telescope was built to answer. The telescope is designed to last at least this long, with margin for error; 10 years is how long they expect the fuel to last.
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  6. 5 years is the length of the primary mission. That's how much time they need to answer the questions this telescope was built to answer. The telescope is designed to last at least this long, with margin for error; 10 years is how long they expect the fuel to last.
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  7. it's 6 months, not a year.
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  8. not of the whole process I guess, but I've seen time lapses of e.g. the sunshield deployment test.
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  9. JWST has a refueling port. What we don't have yet is a spacecraft that can safely approach JWST without damaging the sunshield.
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  10. 5 years was the worst-case scenario (and enough to fulfill the primary science objectives), 10 years the expected lifetime, and after a bettter-than-expected launch we're already at 20 years.
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  11. You're right, JWST has a refueling port. What we don't have yet is a spacecraft that can safely approach JWST without damaging the sunshield.
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  12. JWST does have a refueling port. What we don't have yet is a spacecraft that can safely approach JWST without damaging the sunshield.
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  13. They don't have to adjust for distance, but they will recalibrate occasionally (or rather, check to make sure the calibration is still correct).
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  14. The JWST science team allocates time to researches. Any astronomer can apply for observation time. The first 6 months of observation time have been allocated and published.
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  15. we've had several IR missions after IRAS: ISO, Herschel, WISE.
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  16. no.
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  17. Earth is hit by about 5200 tons of debris every year. With the difference in size between Earth and JWST, you can calculate JWST will be hit by nanograms of debris every year.
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  18. The mission ends pretty soon after it's out of fuel. Without fuel, it becomes harder and harder to keep the spacecraft pointed correctly.
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  19. Parts of the spacecraft (including the batteries) are much warmer than that - the sun-facing side is at +100 ºC.
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  20. it should be 6 months.
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  21. JWST has a refueling port. What we don't have yet is a spacecraft that can safely approach JWST without damaging the sunshield.
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  22. JWST has a refueling port. What we don't have yet is a spacecraft that can safely approach JWST without damaging the sunshield.
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  23. JWST has a refueling port. What we don't have yet is a spacecraft that can safely approach JWST without damaging the sunshield.
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  24. The Ariane 5 was designed in the 1980s. Retrofitting cameras would mean redesigning the communications system to carry way more data, which means requalifying the rocket, which they're not going to do for the last 5 Ariane 5 missions.
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  25. JWST is a joint NASA-ESA-CSA project. The launch was part of ESA's contribution to the cost.
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  26. Yes. L2 is a good position: far away from the manmade debris in low Earth orbit. They will get the occasional hit from microscopic dust, on the order of nanograms per year.
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  27. They'll need more than a Starship. Starship's thrusters would damage the sunshield, so they'll have to build a smaller craft that can approach safely.
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  28. Scientists: we plan for the worst and build in a lot of margin everywhere. The primary mission was 5 years, so the telescope has to last 5 years even if a lot goes wrong.
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  29. Earth is hit by about 5200 tons of debris every year. With the difference in size between Earth and JWST, you can calculate JWST will be hit by nanograms of debris every year.
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  30. Sensors often give us more information than a camera.
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  31. it isn't. Space is very empty, so the chance of serious damage is tiny.
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  32. I suspect we'll see a proposal for a refueling vehicle soon. It's not needed for another 10 years, so no need to develop it while JWST was under construction.
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  33. Cryogenic fuels boil off. JWST uses hydrazine, which is a liquid at room temperature, so there's no evaporation.
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  34. JWST does have solar panels. One thing you can't do with electricity alone is propel a spacecraft (which JWST has to to regularly). The mission length is limited by the amount of thruster propellant: they couldn't add more because of weight limitations. JWST has a refueling port. We don't have a spacecraft yet that can safely approach JWST without damaging the sunshield. 5 years was always the worst-cse scenario, 10 years the consevative estimate. At the moment, after a better-than-expected launch, we're looking at a 20-year mission.
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  35. Earth is hit by about 5200 tons of debris every year. With the difference in size between Earth and JWST, you can calculate JWST will be hit by nanograms of debris every year.
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  36. Yes, JWST has a refueling port. What we don't have yet is a spacecraft that can safely approach JWST without damaging the sunshield.
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  37. Space is really empty, the most likely collisions are with microscopic dust particles which will just create a tiny crater in the mirror. If a primary mirror segment is destroyed, the telescope can still work. JWST will encounter nanograms of dust per year, on average.
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  38. no, it'll take 6 months.
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