STEREO Mission Design Web Site
There's virtually no change in Behind's Feb. 25th lunar transit after today's momentum dump
STEREO launched 2006 October 26 UT; early reports here
Ahead observed from Australia during 2nd perigee Nov. 17 and from Kitt Peak during 4th perigee Dec. 12
Update 78 - February 22, 2007, 23:30 UT
This version updates Behind's trajectory with yesterday's FDF082 orbit solution using 30 days of post-S2 tracking, and also applies the Guidance and Control (G&C's) team's determination of the small (0.086 m/s) delta-V that was applied by a momentum dump that was applied at 14:01 UT earlier today. The previous version updated both Ahead's and Behind's trajectory, with 21 days of post-S2 swingby tracking data; the new trajectory for Behind was virtually identical with the previous one that used data up to Feb. 6. The only change of version #73 over #72 is the replacement of Peter Sharer's movie of the February 25th lunar transit for Behind with one that uses the current latest trajectory, FDF 016, in the "Latest Trajectory Files" Section below. The only change of version #74 over #73 is the replacement of the image of Comet McNaught mentioned below with a movie, including the image that was there before, but much more, showing the motion of the comet and development of the structure in the tail. The head of the comet is overexposed, causing a large vertical bar at its location. Venus causes a smaller vertical stripe across the image, and in the second half of the movie, Mercury enters the view from the right, with only a short vertical bar. The HI instrument cover on Behind was opened on Jan. 11, and right away a spectacular image of Comet McNaught's tail was recorded. Similar images were taken during the following six days; you can see the resulting interesting movie on this STScI Web site. On December 21 at 16h UT, Behind performed an 11 m/sec delta-V maneuver to change its S2 (2nd lunar swingby on Jan. 21) B-plane target to try to arrange a lunar transit of the Sun as seen from the spacecraft on Feb. 25. Goddard Space Flight Center's Flight Dynamics Facility (FDF) provided a new orbit for Behind using 15 days of tracking data up to 20h UT Jan. 5. This trajectory showed that no lunar transit would occur on 2007 Feb. 25 without another delta-V maneuver, so one, similar to the one calculated on Dec. 21, was calculated, a maneuver of 0.8 m/sec that was successfully performed on Jan. 8 at 19h UT. The new trajectory on Jan. 24 & Feb. 6 shows a long transit that is guaranteed now. Update 56 included the first post-S1 orbit solution for Ahead, using 5 days, including only data after the S1 lunar swingby. The new orbit solution shows that Ahead achieved a heliocentric orbit with a drift rate of 21.650 deg./year from the Earth, confirming the pre-swingby determination. As proof that Ahead actually performed a lunar swingby, its HI imager obtained several low-resolution images that you can see here. Update 53 only updated the trajectory for Behind using 5 days of tracking data roughly straddling the S1 lunar swingby. The new post-swingby data shows that the semi-major axis of Behind's orbit was roughly doubled by the lunar swingby, to 489,798 km, as expected. Behind's closest approach to the Moon's center was 11,775.584 km on December 15 at 21:03:10.719 UT. On December 6, we performed a small maneuver with Behind that targeted its current trajectory. At that time, using the tracking data before that maneuver, and the planned data for the maneuver, we calculated that the lunar swingby would be only 328 meters greater and only 0.701 second earlier than it actually occurred. So the maneuver was quite accurate; the target was achieved very well. Late on Wed., Dec. 20, we'll receive enough post-swingby tracking data for Ahead to make a similar assessment for it, although that will be complicated by the momentum dump that imparted about 0.1 m/sec of delta-V on Dec. 13th. The 52nd update included updated trajectory files and removed the P4 perigee prediction files; those predictions are available upon request to anyone who attempted to observe that passage. STEREO was successfully launched from PAD 17B at Cape Canaveral, Florida, with a Boeing Delta II rocket; click here for a picture of the launch and for other official news and information about this exciting mission. The lift-off occurred on 2006 October 26 at 0:52:00.339 UT. Here is a short video clip of the launch. At about 1:14 UT, the Delta 3rd stage completed the injection of the STEREO stack into its highly elliptical orbit and the two separated from each other with a strong spring. Two minutes later, another spring separated the STEREO A and STEREO B spacecraft from each other and at 1:17 UT, all three objects emerged from the Earth's shadow into sunlight. At 1:21:39 UT, over half an hour before the spacecraft rose above the horizon at the Deep Space Network tracking station at Canberra, Australia to give us our first radio communication, Greg Roberts near Cape Town, South Africa started taking images of the spacecraft; as far as I know, he was the first and only person to observe the spacecraft optically after their injection. You can read his account, including his detailed astrometric observations, here, and you can see several of his images, with some description of them, here. In the images, north is down and a little to the left. A short video clip shows 4 of the images in quick succession. THE LATEST TRAJECTORY FILES For those who have Satellite Tool Kit or other software that can read ephemeris files in the JPL "Spice" format, "Spice" files are given below, in both PC binary and plain text "transfer" format. The files extend from 0h UT of 2007 February 12 (from February 20 for Behind) to 2012 July. For those who might need data through the P4 perigee, the previous trajectory files are still available in the P4 perigee section below. STEREO scientists have decided to use what I called previously the "2a" trajectory that had an 11 m/sec delta-V maneuver on Dec. 21 to change the 2nd lunar swingby in a way that permits a transit of the Moon in front of the Sun, as seen from Behind, on February 25th. An animation of the lunar transit as seen from Behind, by Peter Sharer, is here (1.4-megabyte .wmv file) using the Jan. 31st (FDF 045) trajectory; the times of the transit contacts have changed by less than a minute from that trajectory to the current one. Although I find it possible to play it just by clicking on it, it might be better for most to right-click on the link and save the file to your computer, then play it offline. The "transit" trajectory is now the nominal trajectory for Behind, and has been updated here with the Feb. 20th #082 trajectory from Goddard Space Flight Center's Flight Dynamics Facility (FDF) and applying the G&C team's estimate of the delta-V from this morning's momentum dump maneuver, the first one for the Behind spacecraft (separate momentum dumps were not necessary before since they could be worked in with the several delta-V maneuvers for that spacecraft). The nominal trajectory for Ahead, updated with the Feb. 12th #078 trajectory from FDF, is here; it is given as a Sun- centered trajectory rather than Earth-centered since the spacecraft is effectively in heliocentric orbit now. The trajectory propagated to July 2008 shows that 21.649 deg./year is now Ahead's drift rate from Earth. Since there will be no more delta-V maneuvers performed by Ahead, I will no longer update the trajectory here, just letting FDF continue that job. The current Behind trajectory should have the lunar transit on February 25th still lasting from 6:56 to 18:57 UT, with a minimum Sun-spacecraft-Moon angle of 0.041 deg., with 4.7% of the Sun's disk covered by that of the Moon. I calculate Behind's achieved drift rate to be -22.000 deg./year, now exactly the target, but giving more figures, as evaluated on July 30, 2008 (when the spacecraft will be far enough from the Earth to no longer have any significant effect on the drift rate), it is -21.99976 deg./year. Since planetary perturbations cause the drift rate to change by a few thousands of a deg./year, it doesn't make sense to specify the value to more than 3 decimal places. The latest reflection coefficient Cr for solar radiation pressure for Behind was determined to be 1.217, close to the other determinations from earlier this month. Ahead heliocentric - binary format transfer format Behind heliocentric - binary format transfer format Also here is an Excel spreadsheet by Jose Guzman giving trajectory parameters for the nominal trajectories from Dec. 11 to 2012, using the earlier Dec. 11th solutions from FDF; the long-term trajectory for Ahead is slightly different from the Dec. 11th trajectory, which did not include the effect of a momentum dump performed on Dec. 13th, which imparted about 0.13 m/sec of delta-V and thereby increased Ahead's heliocentric drift rate slightly to 21.65 deg./yr. It also increased the S1 lunar swingby distance by 19 km to 7359 km; that event occurred on Dec. 15 at 21:28:02.1 UT. The S1 parameters for Behind were 11,776 km distance at 21:03:10.7 UT. So now the spacecraft are no longer in the phasing orbits and will stay more than 200,000 km from the Earth, at least for several dozen years. For a couple of months following the S2 lunar swingby on Jan. 21st, Behind will be moving slowly "behind" the Earth with good geometry for viewing with large telescopes at about 20th mag. Plots of the STEREO trajectories are in this Power Point file. Another Excel spreadsheet by Jose Guzman gives trajectory information from 2007 Feb. 12, including FDF's trajectory updates of that date. THE LAST PERIGEE PASSAGE ON DECEMBER 12 On December 12 around 9h UT, the two STEREO spacecraft passed through perigee, and were visible for about 5 hour around the times of perigee. Bill Keel, Astronomy Dept., Univ. of Alabama, obtained a trail image of Ahead. He writes: "Attached is a trail image of Stereo-A during last night's perigee passage. This was done remotely with the SARA 0.9m telescope on Kitt Peak. I parked the telescope a few minutes ahead of time at the predicted piece of the track for 0914 UT (using the ephemeris from highorbits.jhuapl.edu, which evidently got the track right within a couple of arcminutes) and took several 60-second exposures, with satellite passage during the third (as expected). This field is about 11.4 arcminutes across with north up. The bright star has V=8.4 from the Tycho catalog (2000: 06 07 55.72 -33 35 43). The range was about 15300 km. I planned another couple of trail intercepts, but the telescope control system detected time-critical observations and chose this time to need a reboot. Jim Albers pointed out this event to me." So far, his is the only observation that I've received. These perigees are very high so unlike the previous perigees, the spacecraft was eclipsed (no passage through the Earth's shadow). The best areas from which the satellites may have been observed were around the locations under the perigee points, but the spacecraft were so high, over an Earth radius altitude, that they were visible from most of the Pacific Ocean, much of North America, northeastern Japan, and northeastern New Zealand. That's for Ahead; Behind was visible from all of Japan, all of New Zealand, eastern Australia, eastern China, Taiwan, Korea, and most of Siberia. The spacecraft were expected to be about 9th magnitude in the Hawaiian Islands, but because of greater distance and lower altitude above the horizon, they were about 11th mag. as seen from the southwestern USA, about 12th mag. as seen from the south-central and southeastern USA, and about 13th mag. as seen from the Midwest. These are calculated magnitudes, based on Broughton's P2 observation described below, and I think could be in error by about a magnitude. The basic perigee data are (based on the December 8th orbit determinations): Spacecraft Ahead Behind Universal Time 8:30:31 9:54:54 Altitude, km 6668 6666 longitude, deg. 174.91 W 163.91 E latitude, deg. 11.36 N 11.06 N Much more about this last (4th) perigee passage is on Jim Alber's Web site. It includes a downloadable Excel spreadsheet that you can use to calculate local predictions (altitude, azimuth, R.A., and Dec.) at 1-min. intervals. He also has nice world maps showing the visibility of the satellites, with color-coded contours showing the brightest magnitude that will be seen. His predictions have now been updated to the latest Dec. 8th trajectory data. He recently said that comparisons with JPL's calculations showed differences of 0.1 and even 0.2 deg. in alt. and az., similar to the errors in my own calculations; my calculations differ from Alber's by about 0.1 deg. He also doesn't know if the software he uses generated J2000 or apparent RA's and Dec's, but to the accuracy stated, that doesn't matter. I calculated the attitude maneuvers for a series of "sunglints" that would flash sunlight from the spacecraft solar panels at selected U.S. cities, and work started on implementing them, but unfortunately the idea had to be shelved as the operations team became very busy with some new requests by STEREO scientists for things to do during the P4 perigee pass. The JPL Horizons Web site is set up to generate local predictions for these spacecraft, but only using an old ephemeris based on the planned maneuvers, not the actual ones. And Jon Giorgini, who is the only one who can update the artificial satellite predictions on that site, is in Antarctica until the end of the year. Unfortunately, the actual spacecraft trajectories are now far from the ones on the Horizons site, so it should no longer be used, and we don't yet have another Web site where these predictions are available. If you have software that can calculate local predictions from orbital elements, you can obtain the orbital elements for Ahead here and Behind here. Two-line elements don't work for these highly-elliptical orbits. Note that the orbital elements in these files are only valid within a day or so of the P4 perigee; especially now they are wrong due to the effects of the lunar swingby (gravity assist) on Dec. 15. The data in these files, and my calculations described below, are from the Goddard Space Flight Center's post-P3 trajectory solutions of December 8th, and now using over 2 days of actual post-manuever tracking rather than just our onboard estimates of what the Dec. 6th A4 maneuver did for Behind. For those who have Satellite Tool Kit or other software that can read ephemeris files in the JPL "Spice" format, "Spice" files are given below, in both PC binary and plain text "transfer" format. The files extend from 0h UT of 2006 December 11 (but from 15h UT Dec. 8 for Behind) to 2012 July. These are from FDF's Dec. 11th trajectories #301 for Ahead and #313 for Behind. After Dec. 15 at 0h UT, you should instead use the more recent trajectories given in the latest trajectory section before this section. Ahead - binary format transfer format Behind nominal - binary format transfer format I have a computer program that calculates the position and circumstances for a specified location, so I have used it to generate predictions for numerous cities and observatories in Hawaii and North America. The output of my program includes the Sun altitude, range to the spacecraft in km, phase angle, and estimated magnitude that are NOW ALSO included in the calculations with the spreadsheet program obtainable from Alber's Web site mentioned above. You can use Alber's spreadsheet to make your own calculation, but if you have any trouble with Excel, I can supply predictions upon request to me at david.dunham@jhuapl.edu. THE THIRD PERIGEE PASSAGE ON NOVEMBER 29 As far as I know, nobody observed the 3rd perigee passage. On November 29 around 19h UT, the two STEREO spacecraft passed through perigee, and were visible for 2 to 3 hours before and after they passed through the Earth's shadow. The best areas from which the satellites could be observed was around the locations under where they enter or exit the shadow. The spacecraft were much higher at this perigee than at the earlier ones, so they were a little fainter, probably around 10th magnitude, but were visible for a longer time and from a larger area. Observers in Europe, Africa, Asia (even Japan and the Philippine Islands were able to see Behind), and the Indian Ocean had a chance to observe them with telescopes; they probably were not bright enough to be seen with binoculars (but note the 8th-mag. observation at the last perigee). The table below gives the shadow entrance and exit times and locations (note that Behind passed through its perigee first): Spacecraft Ahead Behind Shadow Event Entrance Exit Entrance Exit Universal Time 19:56:20 20:15:10 19:18:35 19:38:40 Altitude, km 4448 5944 4270 6015 longitude, deg. 20.98 E 57.46 E 29.92 E 71.01 E latitude, deg. 14.13 N 9.01 S 13.55 N -8.06 S Best areas Europe southern eastern Asia for observation north Asia Europe Indian Africa western Middle East Ocean Indian northeast Ocean Africa The satellites are thousands of kilometers apart near perigee. They spend most of their orbit near apogee, near the Moon's distance; the direction of the apogees is near the direction to the Sun, so they can not be observed then, and can only be seen within a few hours of perigee. Observers towards the Sun from the shadow points (that is, west of the entrance points and east of the exit points) will have better (smaller) phase angles so the satellites will appear brighter for them, but they will have less time in a reasonably dark sky to see them. I have a computer program that calculates the position and circumstances for a specified location, so I used it to generate predictions for numerous cities and observatories in the Eastern Hemisphere. It is not a rigorous or well-tested program, and comparisons using the same data show errors of about a quarter degree when compared with Horizons. However, there is not time to improve the program before the perigee passage; for the test I was able to make, the actual trajectory was 1/4 deg. lower than my prediction (that is, the altitude above the horizon was lower). But my predictions are better then none. I will try to calculate predictions and send them to you on request to me at david.dunham@jhuapl.edu , but before requesting, see if you can find data already computed for your location, or one within a few km of it, below. I've computed predictions for all of the observatories in the Minor Planet Center's list, as of January 2006; for all European asteroidal occultation observers in Jan Manek's list of 2004; for major European and Middle Eastern cities; and for other selected locations throughout the Eastern Hemisphere. The predictions include the equinox 2000 R.A. and Dec., the altitude and azimuth, range, and phase angle at one-minute intervals when the geocentric distance is greater than 20000 km, and at 12-second intervals at lower distances. No data are given when the spacecraft are in the shadow, or if they are less than 5 deg. above the horizon, or the Sun is more than -6 deg. above the horizon. If the spacecraft range is more than 10000 km when it will be fainter, the altitude limit is increased to 10 deg. and the Sun alt. to -9 deg. These predictions have now been removed from this Web site; predictions for any location can be supplied upon request. THE SECOND PERIGEE PASSAGE ON NOVEMBER 17 On November 17 around 12h UT, the two STEREO spacecraft passed through perigee, and were visible for an hour or two before and after they passed through the Earth's shadow. John Broughton in Reedy Creek, Queensland, Australia obtained an image of the Ahead spacecraft. The streak near the center of this 1-second image, about a degree on a side, is Ahead, estimated to be about 8th magnitude. John measured Ahead's position at 13:57:39.8 UT to be J2000 RA 5h 58m 33.97s, Dec. -1 deg. 25' 26.8", accurate to a few arc seconds, but the time accuracy is only 0.2s. The image has north up and is about 5 deg. east of Orion's belt. The bright star to the left (east) of Ahead is 6.8-mag. SAO 132723 while the one in the center top part of the field, directly above (north of) Ahead is 9.7-mag. SAO 132711. John's observation, made from longitude 153 deg. 23' 49" east, latitude -28 deg. 06' 36", height 66m (1966 Australian Geodetic Datum) is the only one during the 2nd perigee passage that I know about so far. The best areas from which the satellites could be observed were around the locations under where they entered or exited the shadow. Observers in southern and eastern Asia, and New Zealand and Australia had a chance to observe them with telescopes; they were not bright enough to be seen with binoculars. The table below gives the shadow entrance and exit times and locations: Spacecraft Ahead Behind Shadow Event Entrance Exit Entrance Exit Universal Time 13:35:31 13:56:54 11:10:33 11:31:52 Altitude, km 2506 3506 2180 3274 longitude, deg. 103.2 E 164.8 E 136.9 E 154.7 W latitude, deg. 27.8 N 16.8 S 26.0 N 15.8 S Best areas India New Taiwan New for observation s.e.Asia Zealand Japan Zealand China Australia Philippine (low in Islands east) China Delta-V Maneuver Start End Start End Universal Time 12:56:00 12:59.0 10:00:00 10:05.0 In addition, observers in the areas under the shadow entrance might see the spacecraft brighten a little as they fire their thrusters for velocity-change (Delta-V) maneuvers. The times of these are also given above. The start times are exact, but the end times are uncertain by several seconds since the maneuvers are terminated by on-board accelerometers that sense when the Delta-V target has been achieved. About 20 minutes before the maneuvers, and a few minutes after them, the spacecraft change their orientation, so a change in apparent brightness might be seen then as well. The purpose of the two maneuvers last week was to target each spacecraft to the first lunar swingby on December 15th, and the Behind spacecraft to the right conditions at the first swingby so that it will have a second lunar swingby on January 21st. The maneuvers were quite successful for this purpose; the Ahead spacecraft is already targeted to the right spot on the "B-plane" at the first lunar swingby so that it will achieve its desired heliocentric orbit, with a drift rate of 21.98 degrees/year from the Earth. The Behind spacecraft has a good first lunar swingby, but is about 15,000 km from the intended target on the B-plane of the much more sensitive second lunar swingby (S2) on 2006 January 21. A small maneuver for Behind will be performed in early December to try to move its S2 B-plane point to the desired target. With Behind's maneuver on December 6, we could reach any point on the S2 B-plane, which is shown in this Power Point file in the first slide, created by Brian Kantsiper and Peter Sharer. The colored areas are parts of the B-plane where the lunar swingby will cause the spacecraft to escape from the Earth-Moon system. The contour lines give the drift rate of the resulting heliocentric orbit from the Earth in degrees per year. The desired curve is -22. Dots, only approximately positioned, on the -22 curve show 11 possible orbits that are illustrated in the last three slides of the Power Point file. The dots, and the trajectories after S2, are color-coded. Some of their key parameters are given in this Excel file. The "2a" trajectory has an aphelion distance that is within the trajectory specifications, while the nominal trajectory does not (see below), and the "2a" trajectory apparently does not have the drawbacks (mainly, longer dwell times near the Earth before departure) of other trajectories that also have low-enough aphelia. Another bonus of the "2a" trajectory is that there will be a lunar transit just over a month after S2, on 2007 February 25. The four contacts would occur at 3:44, 6:20, 14:20, and 16:26 UT, respectively. The Moon will be about 1.6 million km from the spacecraft, so it will subtend 3.6', covering 4.8% of the Sun's disk by area. This transit might be used for instrument calibration. I've updated the Power Point file noted above here, using the latest trajectories and now showing just the nominal and 2a trajectories for Behind, and now also the Mercury transit trajectory for Ahead. The green "2a" trajectory has a short red segment that marks the location from which the lunar transit will occur. The names of the DSN tracking stations appear in the middle (at the Earth) of these views from our orbit design software; since I will need those for later calculations, I did not remove them. THE FIRST PERIGEE PASSAGE ON NOVEMBER 5/6 The spacecraft passed through the Earth's shadow during their perigee passes around 8h UT of 2006 November 6. A table below gives the shadow entrance and exit times and locations: Spacecraft Ahead Behind Shadow Event Entrance Exit Entrance Exit Universal Time 8:59:14 9:20:18 7:34:50 7:55:54 Altitude, km 1665 2208 1662 2210 longitude, deg. 165.7 E 107.9 W 173.1 W 86.7 W latitude, deg. 27.2 N 15.4 S 27.4 N 15.4 S The shadow entrances were over the central Pacific Ocean while the shadow exits were off the northwest coast of South America. Observers in Central America and northwestern South America might have seen the spacecraft from the time they exit the shadow until twilight becomes too bright; Greg Roberts' observations show that they might sometimes get as bright as 6th magnitude, but more likely they will be about 8th magnitude. I have heard of no successful observations. Also during the first perigee, the third stage booster rocket must have burned up in the Earth's atmosphere. This was expected to occur at 0:48 UT over the Atlantic Ocean about 1000 km east- northeast of the Virgin Islands, where the beginning of the reentry might have been briefly visible just above the east-northeastern horizon. The reentry point was at about longitude 53.5 deg. W, latitude 22.4 deg. north. The time could be in error by several minutes and the longitude might be off by 5 degrees or so; if the error is on the late side, observers in the Virgin Islands might have had a spectacular view of the reentry low in the northeast. I know of no observations of this event. The JPL Horizons ephemeris generator Web site has been updated with the November 14th trajectories so you can compute the paths in the sky for your location. But this won't work for the P4 perigee passage; see above, and use of the Horizons Web site is not recommended until sometime in January when Jon Giorgini returns to update it. Although the spacecraft will be impossible to observe most of the time for the next few weeks, there will be times when they can be seen, for an hour or two before and after going through shadows at the four perigees before the first lunar swingby keeps them far from Earth. And as they drift away from the Earth-Moon system, for a month or two a few of the major observatories should be able to image the spacecraft, especially Behind which will have an elongation from the Sun greater than 90 deg. for a few months after its last lunar swingby. Maybe we can arrange some sunglint maneuvers during this time that would make Behind visible with small telescopes. OCTOBER 30TH MANEUVERS NEAR APOGEE SUCCESSFULLY RAISE PERIGEE November 14th maneuvers successfully changed the orbit planes The delta-V maneuvers performed on 2006 October 30, each about 11.6 m/sec, successfully raised the perigees of both spacecraft to a safe 500 km altitude. At 17h UT October 31, the Flight Dynamics Facility at Goddard Space Flight Center delivered their first post-maneuver trajectory, and we used it to calculate the new perigee distances; here are the results. Since these "survival" maneuvers, much larger maneuvers were performed on November 14th that changed the planes of the orbits as part of the targeting of the first lunar swingby on December 15. Early indications show that the maneuvers were quite accurate, possibly as accurate as the A1 burns, which we now know from tracking data hit their target delta-V's with less than 0.1% error. STATUS REPORTS FROM STEREO'S FIRST WEEK During the first week, STEREO Operations compiled daily status reports giving highlights of activities by the various STEREO groups, including information about the trajectory from Mission Design. After the first week, weekly reports will be provided. On November 2, small engineering delta-V's were performed, amounting to 0.2 meters/second, which successfully tested and calibrated the "C" group of thrusters that will be used for a maneuver at the 2nd perigee on November 16/17. The next maneuvers, on November 14, will change the plane of the orbits. Links to the reports (Word files) are below. 2006 November 1 - Day 7 after launch 2006 October 31 - Day 6 2006 October 30 - Day 5 2006 October 29 - Day 4 2006 October 28 - Day 3 2006 October 27 - Day 2 2006 October 26 - Day 1 BEHIND APHELIONS MAY BE TOO HIGH, NOMINALLY OUT OF SPEC; WAYS TO LOWER THEM The mission orbit for Behind has short violations of the maximum aphelion distance that we knew were probable from calculations of the late October launch trajectories in early September. There is also a violation of the minimum Sun distance, but it occurs during the sunward-pointed outer loop apogee between the S1 and S2 lunar swingbys, before the agreed-upon routine science operations would commence. The extremes occur because S2 is in January, when the Earth is near perihelion. The excursions pose no thermal or other danger to the spacecraft, but the occulting disk of the coronagraph was designed for the agreed-to limits. Mission Design has begun studying options to lower the maximum aphelion distance; this is possible at the expense of either spending a month or so on the wrong side of the Sun-Earth line near the L2 libration point after S2, or spending one or two extra months in the outer loop between the two lunar swingbys (which makes the "ejection" from Earth later, away from Earth's perihelion). The decision on which way to procede needs to be made in about two weeks, in time to incorporate into the design of the 2nd perigee maneuver on November 17. Some details (orbit view and chart) are here, in Peter Sharer's two-page Power Point presentation. But the small excursions turn out to be of little concern to the STEREO scientists, so the nominal trajectory will be used. HISTORY OF THE 2006 LATE OCTOBER LAUNCH WINDOW Curiously, we did not even know about the possible late October launch window until late July. Click here for my first message suggesting it, and some recent comments about the rush to get the late October launch to become a reality. ________________________________________________________ STEREO MISSION DESIGN/NAVIGATION REVIEW, 2005 OCTOBER 12 This site is for making accessible the presentation files for the STEREO Mission Design/Navigation Review that was held in MP3-E183 of the Johns Hopkins University's Applied Physics Laboratory at 7707 Montpelier Rd., Laurel, MD 20723 on Wednesday, October 12, 2005. The members of the review panel, and planned agenda, can be found in the introduction item at the top of the list of presentation files below. We now have documents that address or close the action items of the Review that will be posted here next week. A Mission Integration Working Group (MIWG) meeting is scheduled for Kennedy Space Center (KSC) on May 25th; the Mission Design presentation for the FOR (with explanation and link in the next paragraph) will likely be modified only slightly for that MIWG. Sometime in June, after the MIWG, we will probably have an update to the Mission Design/Navigation Review to focus on the current launch plans and trajectories. This 25th update of 2006 July 7 closes action item #4 and adds here a link to Mission Design's presentation for the May 24th MIWG meeting that includes the latest version of our viewgraphs. In addition, backup viewgraphs were prepared to show how adjusting the number of phasing loops and other strategies could be used to handle very large injection underburns, and these additional viewgraphs showed how we could recover even from 3-sigma underburns at 95% PCS. Currently, the planned launch for STEREO will be not earlier than (NET) August 1, 2006. The 24th update closed more of the action items and updates that section near the bottom of this page. The 23rd update only added the Mission Design presentation, the latest version that was shown at the Flight Operations Review on May 3, since only an earlier April 24th version was in the printed version and also on the CD that was distributed at the review. Just the changed and added figures are here. The 22nd update added a section near the bottom with details about action items and recommendations from the review, a document that describes their current status, and documents that address or close several of the action items and recommendations. The only item added over the 19th update on 2005 December 12th is the addition of this Mission Design presentation for the Flight Operations Review (FOR) that will be held at APL on May 3 and 4 (updated to the final version of April 25 with this 21st update). It is the first presentation of Mission Design information for the current STEREO Launch window of 2006 July 22 - August 6. The only item added over the 17th update on October 13th is the addition of these minutes of the meeting by T. Strikwerda. During the 1st week of December 2005, the launch date for STEREO was slipped to the May 26 - June 8, 2006 launch window. New DTO inputs were computed for this launch window, and a presentation for it, giving information similar to that given for the 4th and 5th presentations below, was given at the STEREO Mission Integration Working Group (MIWG) meeting at KSC on Dec. 7. A few backup slides were also prepared. These are the only items added with the December 12th update. Introduction - Tom Strikwerda - 3rd (Agenda) Slide Updated Oct. 10 Mission Design Overview - David Dunham Heliocentric Mission Orbits - David Dunham Launch Phase, April 11-May 9, 2006 - Jose Guzman Phasing Orbits for April 11-May 9, 2006 - David Dunham, updated Oct. 11 Early Operations Overview - John Eichstedt Monte Carlo Studies, Launch Dispersions, etc. - Jose Guzman Maneuver Contingency Plans - David Dunham, slide 7 inserted Oct. 11 Finite Burn Modeling - Jose Guzman Delayed Launch Options, late May - early Oct., 2006 - Jose Guzman Navigation Overview - Michael Mesarch Navigation Operations - Neil Ottenstein, p. 14 updated Oct. 6 Navigation Covariance Analysis - John Lorah, updated Oct. 6 Navigation Testing and Status - Neil Ottenstein For the phasing orbits, on slide #11 (originally prepared for the CDR), it is pointed out that the curve is similar, actually better, for other launch dates, and on slides 13 and 20, an extraneous "t" before "Green" has been removed from the footnote. The pages of John Lorah's Navigation Covariance Analysis that were updated from Oct. 5 to Oct. 6, with the changes indicated in red, are here. Backup Information From update 14 to this, only the last backup item has been added. STEREO Mission Design Specification document (Feb. 2003) - Peter Sharer - added Oct. 2 Separation Analysis Paper AAS 03-553 by Peter Sharer - added Oct. 5, 7 pm Some direct heliocentric injection trajectories - added Oct. 5, 7 pm Delta-V Budget and Margin by Jose Guzman - added Oct. 7, 4 pm Science Instruments - added Oct. 7, 7 pm April 26 - May 9 launch perigee shadows by Jose Guzman - added Oct. 7, 7 pm CDR Propellant Budget by George Cancro - added Oct. 7, 7 pm G&C Instruments - added Oct. 7, 7 pm G&C Momentum Dumps - added Oct. 7, 7 pm G&C P2 Delta-V Monte Carlo Study by Courtney Ray - added Oct. 7, 7 pm P2 Delta-V Reconstruction by Jose Guzman - added Oct. 10, 5 pm Comparisons of PMA & DTO TIP orbits by Jose Guzman - added Oct. 7, 7 pm Mission Design Configuration Control by Jose Guzman - updated Oct. 11, 5 pm Maneuver Verification form - added Oct. 13, 7 pm FDF/APL Trajectory Comparison - added 2006 May 2 pm _____________________________________________________ Action Items and Recommendations The review panel wrote nine action items and made five recommendations following the review. They are in this pdf document, the minutes of the mission design and navigation review distributed by Tom Strikwerda on November 7, 2005. The status of the action items and recommendations, as of June 27, 2006, is in this Word document by David Dunham, modified from Neil Ottenstein's review action item status report in his STEREO Navigation FDF task status report for April 2006. The intention was to close many of the action items with the help of this Mission Design Flight Manual. Some documents that address specific action items and recommendations are listed and linked to below, giving action item responses and approvals, if closed, and remarks, if not. Action Item 1, closed Action Item 2, closed Action Item 3, closed Action Item 4, closed Action Item 5, closed Action Item 6, open Action Item 7, open - Mission Rehearsal Tests #2 and #4 were successful for maneuver design and implementation. The smaller additional Operational Readiness Tests (ORT's) between Mission Design and FDF for maneuver design will be conduced by July 14 as the design for nominal trajectories for launch on Aug. 1-6. Action Item 8, closed Action Item 9, open Recommendation 1, closed Recommendation 2, open - Additional A1 burn simulations will be performed as part of the ORT's for Action Item 7. Complete A1 burn simulations were conducted as part of Mission Rehearsal Test #4 on June 17-20, 2006. Recommendation 3, open - This is not an issue for the current launch window, and more information that may be good enough to close this is in this action item summary. Recommendation 4, open Recommendation 5, open - Neil Ottenstein reports that current GTDS testing covers the use of Deep Impact data to test ramped phase tracking. _____________________________________________________ For the benefit of those attending the meeting from out of state, this APL Web site has maps and other useful information. If you can't attend in person, we should be able to set up at least a conference call for parts of the meeting; if interested in doing that, send me phone numbers where you can be reached and the presentations in which you are interested. The number of the speaker phone in the conference room is 240-228-0133 and my cell phone number is below, for phoning in questions, or if there are any problems. David Dunham phone 240-228-5609; cell 301-526-5590; fax 240-228-0355