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planet4589's profile
Jonathan McDowell
Jonathan McDowell
Jonathan McDowell
Verified account
@planet4589

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Jonathan McDowellVerified account

@planet4589

Astronomer at (but not speaking for, duh) the Center for Astrophysics, working on Chandra and quasars, and commenting on space launches and space activities.

Somerville, MA, USA
planet4589.org
Joined January 2009

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    1. Jonathan McDowell‏Verified account @planet4589 Jan 27

      Jonathan McDowell Retweeted LeoLabs, Inc.

      The NASA/NIVR IRAS satellite and the NRO/USN POPPY 5B satellite (aka GGSE 4) are predicted to make a close approach on Wednesday. POPPY 5B has 18-metre-long gravity gradient booms so a 15-to-30 metre predicted miss distance is alarminghttps://twitter.com/LeoLabs_Space/status/1221908253627412480 …

      Jonathan McDowell added,

      LeoLabs, Inc. @LeoLabs_Space
      2/ On Jan 29 at 23:39:35 UTC, these two objects will pass close by one another at a relative velocity of 14.7 km/s (900km directly above Pittsburgh, PA). Our latest metrics on the event show a predicted miss distance of between 15-30 meters. pic.twitter.com/Hlb1KeQ50U
      Show this thread
      11 replies 164 retweets 342 likes
      Show this thread
    2. Jonathan McDowell‏Verified account @planet4589 Jan 27

      Mass of IRAS is 954 kg. Mass of POPPY 5B is only 85 kg.

      2 replies 3 retweets 30 likes
      Show this thread
    3. Jonathan McDowell‏Verified account @planet4589 Jan 27

      IRAS, launched in Jan 1983, made the first detailed all-sky survey of the infrared sky and the IRAS catalog is still the definitive all-sky list of IR sources. The 0.6m beryllium telescope was cryo-cooled to 3K by 73 kg of liquid helium. The satellite was deactivated in Nov 1985

      3 replies 5 retweets 36 likes
      Show this thread
    4. Jonathan McDowell‏Verified account @planet4589 Jan 27

      The IRAS project was a joint venture between @NASAJPL and the Dutch research agency Nederlands Instituut voor Vliegfulgontwikkeling en Ruimtevaart (NIVR).

      4 replies 3 retweets 27 likes
      Show this thread
    5. Jonathan McDowell‏Verified account @planet4589 Jan 27

      POPPY 5B was launched in May 1967 as part of a four-satellite signals intelligence cluster operated by the US Naval Research Laboratory. It operated until May 1972.

      1 reply 1 retweet 28 likes
      Show this thread
    6. Jonathan McDowell‏Verified account @planet4589 Jan 27

      POPPY 5B orbit is 895 x 910 km x 70.0 deg; IRAS orbit is 880 x 905 km x 99.0 deg (sun-synch with 1747 local time descending node).

      2 replies 2 retweets 21 likes
      Show this thread
    7. Jonathan McDowell‏Verified account @planet4589 Jan 27

      My own quick calculations with the TLEs confirm a pass within 2 km at 14.7 km/s relative velocity at about 2339:35 UTC Jan 29. The LEOLabs tracking data is likely to be more accurate.

      2 replies 5 retweets 28 likes
      Show this thread
      Jonathan McDowell‏Verified account @planet4589 Jan 27

      Here is a ground model of the same ("multiface") design as POPPY 5B, with the booms not extendedpic.twitter.com/xVDXh09r5D

      4:02 PM - 27 Jan 2020
      • 2 Retweets
      • 28 Likes
      • RabidOtter SemprePhi Kevin Rowell Chris Ostrom 𝙀𝙣𝙯𝙤 𝙋𝙚𝙥𝙚 🇮🇹🇪🇺🌍🏴‍☠️ Autistic Space Hamster says: Black Lives Matter! KarenTheCatServant Amos Bairn Simon Porter
      2 replies 2 retweets 28 likes
        1. New conversation
        1. Jonathan McDowell‏Verified account @planet4589 Jan 27

          Here is an illustration of an earlier model of the series (POPPY 4D) with the booms extended.pic.twitter.com/gOFHEN6hR5

          2 replies 2 retweets 30 likes
          Show this thread
        2. Jonathan McDowell‏Verified account @planet4589 Jan 27

          And here is artwork of IRAS (Infrared Astronomical Satellite) in orbit.pic.twitter.com/raFag1Do7W

          6 replies 3 retweets 37 likes
          Show this thread
          3. End of conversation
        1. Homem do Espaço‏ @HomemDoEspacoBr Jan 27
          Replying to @planet4589 @NASAJPL

          with ammonia micro-thrusters

          0 replies 0 retweets 1 like
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