1 00:00:00,000 --> 00:00:04,000 tone 2 00:00:04,020 --> 00:00:08,000 Hi, folks, I'm Joe Gurman, the STEREO project scientist 3 00:00:08,020 --> 00:00:12,030 at NASA's Goddard Space Flight in Greenbelt, MD. 4 00:00:12,050 --> 00:00:16,040 STEREO, or the Solar Terrestrial Relations Observatory, 5 00:00:16,060 --> 00:00:20,050 is a NASA mission consisting of 2 spacecraft, orbiting the sun in orbits just 6 00:00:20,070 --> 00:00:24,090 inside and outside the Earth, with the objective of learning more 7 00:00:24,110 --> 00:00:28,130 about solar activity and how it propagates through the heliosphere. 8 00:00:28,150 --> 00:00:32,130 Today, we are talking about what is going with the STEREO mission. 9 00:00:32,150 --> 00:00:36,160 over the next year and a half or so, that includes both a period of superior 10 00:00:36,180 --> 00:00:40,170 conjunction, when the spacecraft on the other side of the sun from the Earth, 11 00:00:40,190 --> 00:00:44,180 and also a longer period on the other side of that, when the Earth 12 00:00:44,200 --> 00:00:48,200 the high gain antennae will have to off-pointed for once 13 00:00:48,220 --> 00:00:52,220 opting toward the Earth because of a thermal problem. 14 00:00:52,240 --> 00:00:56,240 During those weeks of superior conjunction for each spacecraft, the noise level 15 00:00:56,260 --> 00:01:00,260 of getting their signals back will be too high, simply because 16 00:01:00,280 --> 00:01:04,270 the antennae here on Earth will be looking at the sun as well as the spacecraft. 17 00:01:04,290 --> 00:01:08,300 During that period, we won't be able to communicate with the spacecraft, 18 00:01:08,320 --> 00:01:12,320 and after about 3 days, there's a timer on the spacecraft that will go off 19 00:01:12,340 --> 00:01:16,340 and put it in safe mode. It will also turn off the power 20 00:01:16,360 --> 00:01:20,350 to the instruments. And that's a period of about 15 weeks on the ahead spacecraft 21 00:01:20,370 --> 00:01:24,360 and 9 weeks on the behind spacecraft. Fortunately, 22 00:01:24,380 --> 00:01:28,370 those periods don't overlap. In August 2014, 23 00:01:28,390 --> 00:01:32,390 we will reach a situation where the high gain antennae on the STEREO spacecraft 24 00:01:32,410 --> 00:01:36,410 will be pointing back toward Earth, but seeing too much of the sun. 25 00:01:36,430 --> 00:01:40,420 That means that the feed of the focus of that antennae will be getting too 26 00:01:40,440 --> 00:01:44,440 hot, and we will have to start off-pointing the antennae, and using the weaker 27 00:01:44,460 --> 00:01:48,460 so-called side lobes to communicate with the Earth. That means we can't 28 00:01:48,480 --> 00:01:52,460 get back as much data in the given amount of time as we could before. 29 00:01:52,480 --> 00:01:56,480 We are going to be carefully cherry-picking the which data we send back 30 00:01:56,500 --> 00:02:00,500 during that period. That's a period of about 16 months on the ahead spacecraft 31 00:02:00,520 --> 00:02:04,530 and 14 months on the behind spacecraft, and it will take us 32 00:02:04,550 --> 00:02:08,560 to approximately the beginning of 2016 when we can resume 33 00:02:08,580 --> 00:02:12,600 normal operations on the main lobe of the antennae. During those periods of 34 00:02:12,620 --> 00:02:16,610 time, we will be down to about 7.4 kilobits a second 35 00:02:16,630 --> 00:02:20,620 and 1.7 kilobits a second science telemetry. 36 00:02:20,640 --> 00:02:24,640 It's worth noting that even the smaller of the 2 numbers is a 37 00:02:24,660 --> 00:02:28,680 factor of 10 greater than the rate we currently get back from Voyager 2, 38 00:02:28,700 --> 00:02:32,690 which is at the outer limits of the solar system. Those data are certainly 39 00:02:32,710 --> 00:02:36,720 worth taking, and we believe the data from STEREO are worth taking too 40 00:02:36,740 --> 00:02:40,740 as STEREO gives us the only view of what's going at the far side of the sun 41 00:02:40,760 --> 00:02:44,750 and in the heliosphere on that side as well. 42 00:02:44,770 --> 00:02:48,750 beeping 43 00:02:48,770 --> 00:02:55,489 beeping