An image from each of my remote cams during the awesomely successful Iridium-6/GRACE-FO launch at Vandenberg AFB. @Teslarati @MiopsTrigger #spacex #Iridium6 #Falcon9
0 FALCON 9 DEB1 43483U 18047H 18146.73897838 .00064663 00000-0 25203-2 0 99942 43483 89.0445 238.5947 0013792 240.1102 119.8751 15.25615106 468
Interestingly, SpaceTrack lists also eighth object on orbit, cataloged as object H, identified as FALCON 9 DEBRIS - separated on similar orbit as GRACE-FO 1&2.2018-047H 2018-05-26 17:44 UTC - 479/498km/89.04°Quote0 FALCON 9 DEB1 43483U 18047H 18146.73897838 .00064663 00000-0 25203-2 0 99942 43483 89.0445 238.5947 0013792 240.1102 119.8751 15.25615106 468
For Iridium NEXT followers, our five Launch 6 satellites are all performing very well. The first 2 (SV110 and SV147) will go into service in two weeks, and the 3rd (SV152) will go into service about 5 days later, completing plane 6 (and 3 full planes!). Other 2: in-orbit spares
Falcon 9 fairing halves deployed their parafoils and splashed down in the Pacific Ocean last week after the launch of Iridium-6/GRACE-FO. Closest half was ~50m from SpaceX’s recovery ship, Mr. Steven. http://instagram.com/p/BjdAcCuFegz
QuoteFalcon 9 fairing halves deployed their parafoils and splashed down in the Pacific Ocean last week after the launch of Iridium-6/GRACE-FO. Closest half was ~50m from SpaceX’s recovery ship, Mr. Steven. http://instagram.com/p/BjdAcCuFegzhttps://twitter.com/SpaceX/status/1002268835175518208
JPL News | June 11, 2018GRACE-FO Turns on 'Range Finder,' Sees Mountain EffectsRecently Launched Twin Satellites Create 'The Himalaya Plot'Less than three weeks after launch, the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission has successfully completed its first mission phase and demonstrated the performance of the precise microwave ranging system that enables its unique measurements of how mass migrates around our planet.The twin spacecraft launched May 22 from California's Vandenberg Air Force Base. NASA and German Research Centre for Geosciences (GFZ) engineers and mission controllers at the German Space Operations Center in Oberpfaffenhofen then spent the first few days completing the mission's launch and early operations phase and moving into an 85-day in-orbit checkout period. Science operations will begin when that period has been successfully completed.During the initial phase, the twin GRACE-FO satellites were maneuvered into their operational orbit formation approximately 137 miles (220 kilometers) apart. Spacecraft systems were powered on, checked out and found to be performing as expected. Engineers also activated both primary instruments: the accelerometers, which measure forces on the satellites other than gravity, such as atmospheric drag or solar radiation pressure; and the microwave ranging instruments, which precisely measure the distance changes between the two satellites as they orbit Earth. Variations in Earth's gravity field caused by changes in the distribution of Earth's mass on and beneath the planet's surface -- such as groundwater withdrawal and ice melt -- cause the distance between the two satellites to vary ever so slightly.The GRACE-FO microwave ranging instruments allow distance measurements with a precision better than one micron -- less than the diameter of a blood cell, or a tenth the width of a human hair.During any single orbit of the satellites, some of the largest gravity variations on Earth seen in the satellite ranging data are due to massive mountain ranges. To demonstrate the initial performance of GRACE-FO's microwave ranging system, the team examined its measurements of changes in the distance between the two satellites as they flew over the Himalayas. The results are shown in a figure that team members dubbed "The Himalaya Plot," which may sound like the name of a mystery movie. However, the figure's working name actually refers to the distance changes measured by the microwave ranging system as the satellites flew over the mountains. The plot's wavy lines show how the distance between the satellites varies as the satellites pass over oceans, land areas, and particularly mountains as they orbit Earth. The observed inter-satellite distance changes, which can be as large as hundreds of microns, are in good agreement with expectations. These results give the team confidence that the mission's key microwave ranging system is performing well.By measuring even minute changes in distance between the satellites, GRACE-FO can detect the month-to-month variations in Earth's gravity field caused by the movement of mass as small as about a half-inch (1 centimeter) of water over an area of about 200 miles (320 kilometers) in diameter.GRACE-FO data will provide unique insights into Earth's changing climate, including large-scale changes in our planet's ice sheets and glaciers; Earth system processes that define our environment, such as droughts and earthquakes; and even the impacts of some human activities, such as changes in the levels of aquifers resulting from pumping underground water for use in agriculture. GRACE-FO observations promise to provide far-reaching benefits to society.For more information on GRACE-FO, visit:https://www.nasa.gov/gracefo
“We had worked for eight years to get to this point, so naturally we were a bit nervous. The laser instrument and its optics are quite delicate. If we had made any design mistake or if anything had been damaged during the launch, there would’ve been no way to fix it,” says Dr. Vitali Müller, a postdoc in the space interferometry research group at the AEI.During the next night, the researchers received the good news: the spacecraft saw several split-second “flashes” during the spiral scans, meaning that the laser instruments and optics had withstood the accelerations during the rocket launch. At 3 a.m. that morning the numbers were crunched and settings to establish a continuous laser link were uploaded to the satellites soon after.Laser Ranging Interferometer running in science modeAt 3 p.m. on 14th of June, the latest downlink from GRACE Follow-On confirmed that the LRI was running in science mode on the first attempt and was delivering its first measurements. The interferometer has been running and has been taking data continuously since then, after a brief reconfiguration the following day.
Since June 14, when contact was established with the satellites, scientists have been testing the laser range-finder system. And, to put it simply, it absolutely smashes the design specifications. Over a time period between 5 and 1,000 seconds, the system should be able to detect distance changes of 2 to 40 billionths of a meter between two satellites that are separated by 220km. However, the team reports sensitivity as low as 300 trillionths of a meter. To put this in perspective, the radar system on the original GRACE was sensitive to changes at about the 10 micrometer level.How do you achieve this sort of accuracy? In short, with lasers. More seriously, a laser beam on the master satellite is stabilized to have a very precise frequency. That laser is shot at the slave satellite. This in itself is an achievement because the laser has to be continuously aimed in the right direction (the radar system manages this with a fixed antenna). The slave satellite uses the incoming light (all 25nW of it) to do two things. First it uses a tiny amount to check that the laser is pointing in the right direction. The remainder of the light is used to set the phase of its own laser, which is sent back to the master satellite—the received laser light is too weak to just be reflected back.The light that is received at the master acquires a phase shift relative to the transmitted light that is proportional to the distance between the two satellites. Since the distance is continuously changing, this is measured as an additional frequency in the received laser spectrum. Hence, a frequency measurement of the incoming laser spectrum becomes a measurement of distance, which, in turn, becomes a measurement of acceleration due to gravity.In the short term, this means that GRACE-FO data will be even better than expected, and the modelers are going to have to get back to work. In the long term, it means that more of the technology for LISA will be validated with the additional benefit of a long-term robustness study. In the very short term, it gave me some good weekend reading.
