FINAL PHASE OF SPACE SHUTTLE REENTRIES
by Paul D. Maley NASA Johnson Space Center Astronomical Society, Houston Texas USA
NOTE: THIS WEB PAGE WAS USED BY OBSERVERS IN CENTRAL AMERICA DURING THE FINAL FLIGHTS OF THE AMERICAN SPACE SHUTTLE.
Fig. 1. Space Shuttle DISCOVERY in orbit as seen from ISS August 2005. Courtesy NASA.
Future Space Shuttle missions are planned to reenter the earth’s atmosphere over Central America on nominal trajectories into the primary landing site at Kennedy Space Center (KSC) in Florida. Based on the various possible reentry flight paths, any part of Central America could experience a ground track that *might* pass over it during this time. The farthest EAST area of visibility (that is, where the maximum elevation above the WESTERN horizon is 15 degrees) would be Panama City, Panama. Therefore no visibility is likely from east of Panama City.
Fig. 2. Central America region where overflights of the Space Shuttle are likely to be seen.
A rather spectacular viewing opportunity for those persons located beneath and about 80 miles on either side of the reentry ground track is possible. As the Shuttle descends into the atmosphere at an altitude of 80 miles (129km) it is moving at Mach 24 (24 times the speed of sound). By the time it reaches Central America it is traveling about 16 times the speed of sound and can appear brighter than the brightest star or planet in the sky. A long contrail will be left in its wake lasting up to 2 minutes in duration. This is truly one of the most beautiful visual phenomena that a person could be lucky enough to witness! But there is more to it than that.
Fig. 3. Camcorder image showing a typical shuttle reentry. Image by P.Maley.
A volunteer ground observer group called the Central American Reentry Observers Network (CARON) is being created that would be intercept and collect information that would possibly be of use to NASA. The NASA Johnson Space Center Astronomical Society has offered to act as a clearing house for reentry reports and to select those which can be best used to assist in the analysis of the final phase of the Shuttle mission. Volunteer observers wanting to be part of CARON should have email and internet access in order to be aware of the ground track (that is, the area over Central America where the shuttle is expected to pass) and the precise day/time of the expected event. While there is no guarantee your data will be used by NASA, we will consider specific reports provided they conform to the specifications below.
STS-115 CROSSES GUATEMALA SEPTEMBER 21, 2006
The first implementation of CARON observations in the region occurred for STS-115. Limited observations were made from Guatemala at between 10:02 and 10:03GMT. Edgar Castro of the Guatemala Astronomy Association reports the results:
1. Edgar, Rodrigo and Juan Carlos Castro observed Escuintla, Guatemala from 14 deg 19m 43.7s N, 90 deg 48m 02.3s W, altitutde 432m watched the orbiter pass to the west of them and saw it for about 8 seconds. The trail remained visible for about 3 minutes afterwards. Observations were made with both naked eye and 10×50 binoculars and there was no sound heard. The fireball appeared bright, white and left a long brilliant trail as seen from the southern coast of Guatemala under scattered cloudy sky with some intermittent showers.
2. Jorge Solano watched from Guatemala City at 14 deg 37m 00s N, 90 deg 28m24.3s W, altitude 1570m and saw it pass at max elevation above azimuth 250 deg. His visual description is identical to that above but saw it for about 20 seconds and estimated the duration of the visible trail from his location at about 2 minutes. He heard no sonic boom but took the photo below.
Photo #1 of the Orbiter reentry of STS-115 as seen from Guatemala City, Guatemala by Jorge Solano. He used a Panasonic Digital DMC Fz5 camera, 8 second exposure, f/5, ISO 4000. The long exposure time helps to bring out the trail but it also adds to the cloud brightness.
3. Ingrid Zapata observed from Totnicapan, Guatemala at 14 deg 55m0.7s N, 91 deg 26m14.1s W, altitude 2360m. The max elevation was above azimuth 165. Due to clouds she observed the orbiter for only about 10 seconds, yet the trail remained visible for about 3 minutes. Again, no sound was heard but 3 photos were taken.
Photo #2 of the Orbiter reentry of STS-115 as seen from Totonicapan, Guatemala by Ingrid Zapata. A Sony digital camera was used with direct exposure. The weakness of a digital snap like this is that in order to see the head and tail better, integration is needed or a faster lens and darker sky. In both photos, you can also see that there is very limited information that can be obtained with a wide angle lens.
4. Fernando Ixlaj observed near San Marcos, Guatemala at 14 deg 57m59.01s N, 91 deg 46m 54.3s W, altitude 2344m and saw the orbiter reach its maximum elevation above the SE at azimuth 135 deg. His observed duration of the orbiter was 10 seconds and reported the trail visibility lasted 3 minutes. He did hear an explosion like sound about 3 minutes after passage.
The primary benefit of such observations are in the event of an on-orbit repair to damaged Shuttle tiles or other surface materials. Such a repair has never been attempted before. Once a surface repair has been accomplished by the Shuttle crew and the Shuttle is returning home, it is extremely important to be able to characterize the effectiveness of the repair. This can best be evaluated by observing the reentry at the higher Mach numbers (i.e. speeds of the Shuttle during the reentry phase) where heating is maximized. Although the most extreme heating occurs southwest of Central America, there is still plenty of thermal activity as the Shuttle begins its overflight of the region. Reentry could occur in the daytime or at night. The most spectacular viewing occurs in the darkness, while in the daytime it is not likely that the reentry can be seen due to the high background sky brightness. In the day as at night, it is also possible to hear the dull ‘thud’ of a sonic boom as the Shuttle passes over. The Shuttle will appear as a bright moving star like object or fireball with a thin trail of ‘smoke’ appearing behind it very similar to an aircraft contrail. Stars are not visible in the daytime though the Shuttle is expected to be as bright as the planet Venus.
A. DEFINE YOUR LEVEL OF INTEREST
There are several possible levels of interest. See if yours is amongst them.
a. General interest: those people who just want to go out and watch the reentry at their leisure. The reentry can be viewed without optical aid and without any equipment. Simply watch and enjoy.
b. Educational viewing: watch the reentry with the intention of getting a better understanding of the process and explaining it to others including young people and the general public. This is a good school project for all ages. It is also a chance for local TV or newspapers to witness and document the flyover. No equipment is necessary but it helps to have a calibrated watch to be able to know exactly when to look and to have a basic understanding of how to locate directions (north, south, east, west) at night or in the daytime. Knowing the constellations is also a good thing and how to understand the brightness system of stars. This information can be found from basic astronomy books or from the internet.
Observation of the Shuttle brightness with respect to time is also important to note and to record. Since there are usually no other comparable objects that bright, it is best to consult the internet to see which planets are brightest and if they will be in the sky during the expected time of the flyover. The brightest star is Sirius at magnitude -1.
Educational projects that can be done during a Space Shuttle reentry.
1. Photography of the reentry (night time only)
2. Videotaping the reentry (night time only)
3. Listening for the sonic booms (day or night)
4. Detecting effects of the sonic booms on insects (sound travels through the ground faster than through air and so it has been documented that certain insects can ‘hear’ the sound before you do); a seismometer might also work for this experiment but would need to be time correlated with a human observer to compare the arrival time of the sonic boom. (day or night)
Fig. 4. Sonic boom recorded February 1, 2003 over Dallas, Texas after STS-107 passed overhead. Courtesy Geotech Instruments.
c. Science data contributors: This is without a doubt the most important task. Observe and record information on the reentry process and report through CARON. This involves having an accurate source of time signals (short wave time signal receiver) and recording comments on the behavior of the reentry fireball as it moves across the sky in real time. If you do not have an accurate source of time signals, your observations will not be of significant value. A pair of securely mounted binoculars and a portable tape recorder are also required. A telescope might be used in place of binoculars but you will find it quite difficult to track and keep the Shuttle in the field of view unless you have an automated tracking mount with specialized software capable of satellite tracking. Binoculars shold be mounted securely so you don’t have to hold them up continuously. It can become tiresome to hold binoculars non-stop while also making your observation. Use a tripod or other inventive means to support them but so they can still be moved in elevation (meaning “up and down”) and azimuth (meaning “right to left”).
However, it is challenging to track an object that could be moving as fast as 5 degrees per second and any observers in this category must be dedicated and persistent in figuring out how to simulate and practice with a telescope before the reentry. For binocular users, this is not so hard. Perhaps tracking low flying airplanes is a good start. The fireball must be kept in the field of view continuously. The main idea is to start the tape recorder about some minutes before the time the Shuttle is predicted to come up over the horizon and to record the observer’s voice and time signals evenly so that your comments and related time ticks can be heard when the tape is played back. The tape recorder or microphone should be worn around the neck so the observer’s hands are free to move the telescope to track and focus on the fireball. See the Reentry Timeline section below.
If you have to use a telescope we suggest a Dobson design which is easy to move in elevation and azimuth. The telescope aperture should be between 3 and 6 inches with a wide field of view to ease the process of manually tracking the fireball. The telescope should have a small finder telescope that you would use to rapidly acquire the Shuttle, then switch to the main scope.
Fig. D1. Mid-size Dobson telescope. This telescope is too large to use.
Fig. D2. Smaller Dobson telescope easier to maneuver.
Fig. ND1. Example of several types of telescopes that you do not want to use. Note that none have finder telescopes attached.
Even more important is to have a good understanding of where the Shuttle can be viewed from and having a good observation site with a horizon free of obstructions. The Shuttle path will cover a large arc through the sky and finding it first as it is rising above the horizon is very important. If you attempt to lock on to it once it has gotten fairly high in the sky, it may be moving so fast that tracking would prove intermittent or impossible. This is why knowing where to expect to first see it as it is clearing the horizon is so critical. If you have mountains or trees or buildings in the way, tracking with a telescope will not be possible for any length of time.
When viewing through a telescope, the eyepiece should have as wide a field of view as is possible. High power eyepieces must NOT be used since the field of view is so small as to make continuous tracking impossible.
The Shuttle will cross the sky in as little as 90 to 120 seconds depending on where you are located with respect to the ground track. Once you have tried to simulate such fast movement, you will likely agree that mounted binoculars will be much more effective than a telescope.
Fig.5. Shuttle reentry of STS-109 by F.Bruenjes. This is a time exposure low on the horizon. The camera shutter was left open for about 10 seconds and the streak was produced by the moving fireball. The white dots are stars. Landscape is in the foreground.
On the horizon (or just a few degrees above it), the Shuttle will appear as a bright star moving very slowly at first. As it gains altitude the speed will increase, quite rapidly depending on its maximum elevation in the sky with respect to your viewing location. Being directly under the ground track offers great views but tracking it as it moves overhead will be very challenging. Therefore having a site that is 20-50 miles west or east of the ground track is suggested. Use the Pan American highway as the principal road if you plan to drive close to the ground track.
B. WHAT INFORMATION IS IMPORTANT?
The observer watches the fireball for any evidence of small pieces of debris that might be seen moving from the fireball backwards into the trail as it moves through the sky. It is not necessary to follow any fragments, just the fireball. Make comments into the tape recorder if a fragment or fragments appear; note any characteristics such as if there is one or two or more fragments and call out when each one is spotted. Continue to follow the fireball until it is lost. It is hoped that no fragments will be seen, which would be very good news. The shuttle’s protective surfaces are designed to withstand the extreme temperatures of the atmospheric reentry process. However, it is possible that some debris fragments could potentially be shed during the flyover; some of them could be visible in binoculars/ telescopes as point like objects perhaps between +4 and +7 magnitude. Fragments are expected to be quite dim and star-like in appearance.
Fig. 6. Fragment of debris appears behind the fireball in this image from the STS-107 reentry February 2003. Observers with camcorders should use this as an example of the proper field of view and placement of the fireball image. Image by C.Valentine.
Fig. 6A. The position of the fragment 2 seconds after the image shown in figure 6. Image by C.Valentine.
B.1 ESTIMATING BRIGHTNESS
While watching the reentry fireball, your job will be to see and then call out into your tape recorder the moment that a piece of debris appears and its brightness level. The brightness of an object in the night sky is estimated using a system of stellar magnitudes. You should be familiar with the constellations and also the magnitudes of key stars that enable to you to first recognize famous constellations like Orion or asterisms (shapes) like the Big Dipper. The brighter the star, the smaller the value of its magnitude. If you are not familiar already with constellations, you will find learning how to recognize them educational and enjoyable.
One good resource for online star charts is the web site http://www.heavens-above.com that contains predictions on viewing of artificial earth satellites and other astronomical phenomena. The site also has interactive star charts at different scales that will permit the user to identify not only the flight path of an earth satellite through the evening or morning sky but overlays it on familiar constellation backgrounds.
When you enter the site, insert your latitude, longitude and time offset as instructed. Then navigate to the Heavens-Above main page and in the left margin look for “ASTRONOMY” and under that “CONSTELLATIONS”. By clicking that option you can view a table of the 88 constellations. Click the name of a constellation and it will display its shape and identify some of the major stars according to magnitude. However, you should check for the over flight of a satellite (for example Hubble Space Telescope (HST) or the International Space Station (ISS) or perhaps select satellites brighter than a certain magnitude from the site. When satellite viewing predictions are displayed you can then click on a specific prediction in order to view the flight path against the constellation background. That chart will display a more diverse star background with a legend at the bottom showing the sizes of the stars represented by dots according to magnitude. You can then familiarize yourself identifying a 0 magnitude star, then +1 magnitude, etc. until you get down to +6 with your binoculars. Depending on how dark your sky is, it is not unusual for city dwellers to only see down to +3 or +4 magnitude but those living outside large population centers can see down to +6.
Sample charts follow. In figure S1 you see the constellation of Orion in the center. The black dots are stars and white background represents the sky. This is the reverse of what you would expect to see at night.
Fig. S1. Orion star chart. Courtesy Chris Peat.
Orion is best seen in the evening during winter months. Figure S2 shows Cygnus and Lyra, two summer constellations. Note the magnitude legends and you can also see a satellite path marked on each figure. Consulting astronomy books which have better self-instruction on how to locate constellations will let you improve your recognition skills. But you must practice using binoculars in order to identify fainter stars of specific magnitudes. It will be necessary to watch for debris pieces and to try to assign brightness levels to them in real-time. During the reentry you will not have time to look around and compare to stars of known brightness. You must rely on experience achieved in preceding days when you have practiced observing stars in your optics. Estimate brightness to the nearest 0.5 magnitude.
Fig. S2. Several constellations of summer-Lyra, Cygnus, Aquila. Courtesy Chris Peat.
B.2 WHAT HAPPENS IF YOU DO NOT SEE ANY FRAGMENTS?
Suppose you are successful in observing the reentry fireball but do not spot any fragments coming from it. This is important information. In fact, what is not seen is just as important as what is seen. Data will be compared from various observers at different locations. It could very well be that your data might be very critical especially if clouds interfere at other locations. Please report only what you can objectively see in your observation report.
The most significant part of observation, whether accomplished optically or using camcorders, is to ensure that all optics are in proper focus. Some people have better observing abilities than others. For example, a young person’s eyes are usually more peceptive. Do not wear glasses when observing the reentry using optics. If watching only with the naked eye, then this is OK. Making useful observations through binoculars or telescope requires the eyepiece(s) fit snugly in the eye socket(s). You should be sure to focus binoculars before the event to ensure that proper focus is achieved and all stars appear as points of light. If they do not focus after attempting to focus using the center focusing mechanism, try to achieve focus by adjusting each eyepiece until that occurs. The same advice applies to a camcorder except it is preferred that you utilize MANUAL FOCUS in order to ensure that you have control in real time. If AUTO FOCUS is used, it is possible that focus could change during the tracking process; so please, only utilize MANUAL FOCUS.
C. TIME SIGNALS AND RECORDING
A good shortwave radio should be able to receive time signals on a number of key frequencies. Reception depends on conditions of the atmosphere and time of day or night when attempting to receive a particular frequency. The most common are from station WWV broadcasting on 2.5, 5.0, 10.0, 15.0 and 20.0 MHz in the northern hemisphere. Time signals are accompanied by voice announcements indicating the time in Coordinated Universal Time. This is the same as Greenwhich Mean Time (GMT). Local time in Central America is either 5 or 6 hours earlier than GMT. To determine this offset, use an internet search engine such as Google and type in key words ‘time in Honduras’ for example if you were located in Honduras. The result will show you the current time and the GMT offset. You will need this information in section E item 4.
A time ‘tick’ or ‘tone’ is heard every second. Voice announcements occur at the start of each minute and must be recorded in order to be sure that the precise time in hours, minutes and seconds can be determined for your observation. If no voice announcements are recorded (just time tones), this will make reduction more difficult. Radio and tape recorder should both be battery powered. Assure that the tape is rewound to the beginning and that batteries in both devices are fresh. Good quality digital shortwave radios can be obtained from certain internet vendors like E-Bay rather inexpensively. You should also have a watch that is synchronized to the radio.
Fig. 7. Example of digital short wave radio.
If you do not have a time signal receiver, you must find some other mechanism. Here are some sources:
Time Voice Announcer, Washington, DC: 202-762-1401 & 202-762-1069
Time Voice Announcer, Colorado Springs, CO: 719-567-6742
(Long distance time may be delayed).
Digital Time for MODEMS, which operate at 1200 baud, 8N1 only.
From Washington, DC: 202-762-1594
From Colorado Springs, CO: 719-567-6743
Computer access to US Naval Observatory time: http://tycho.usno.navy.mil/cgi-bin/anim
or via http://tycho.usno.navy.mil/what1.html which displays animated GIF clocks
or check: http://tycho.usno.navy.mil/what.html
D. CAMCORDER OBSERVATIONS
Camcorders can be particularly useful tools in recording the overflight especially if they have a ‘night shot mode’ which enhances night time recording ability. But even if the camcorder does not have this mode, as long as it can pick stars of +4 magnitude, you have a good chance to record any small debris pieces that MIGHT happen to appear. We do not expect such pieces to appear, but then that is the objective of this monitoring.
The camcorder should be securely mounted on a tripod and moderately zoomed in to where the fireball is in focus and tracked smoothly. See figure 6 for an example of the image scale with respect to field of view. Keep the fireball in the camcorder view finder to where it is between the center and leading edge of the field of view. The leading edge is illustrated by referring to figure 3 and looking at the lower right corner. Be sure the camcorder has the tape or disc set at the beginning and that you focus it on a star of moderate brightness. The focus is THE MOST IMPORTANT element in the process. You must be sure that if the camcorder is pointed at a nearby object in the process of tracking the shuttle that it does not go out of focus. Focus should be set at infinity and verified by viewing more than one star to be sure it shows as a point image.
Any pieces coming off the Shuttle should flow into the trail immediately behind it. Tracking is most important. Record time signals in the background and be sure that the radio is located close enough to the camcorder microphone to record properly. The camcorder should not be zoomed in and out during the pass. Instead, use the approximate image scale as pictured in figure 3.
E. HOW TO FIND INFORMATION ON THE UPCOMING REENTRY TRACK
There are normally two KSC landing opportunities about 90 minutes apart. Once those are exhausted, it is likely the shuttle might wave off until the following day or land at either Northrop (New Mexico) or Edwards AFB (California) either that day or on the following day if the following day’s two KSC opportunities are also waved off.
To get predictions, check this link beginning 48 hours before the predicted day of landing in order to find information on the Space Shuttle projected ground track for reentry from your location:
Follow these instructions exactly for the reentry predictions. If you deviate and try other options, you may not retrieve the correct data.
1. Click on the INPUT tab
2. Under SATELLITE, select KSCXXX(ENTRY) where XXX is the orbit number. The first one in the pull down list is the first KSC landing opportunity and the next one is the second opportunity.
3. Under OBSERVER LOCATION use the pull down menu to select the STATES option. Then select CENTRAL AMERICA and it will bring up a map of Central America with a number of cities displayed. If you see the city from where you plan to watch, click on that dot; if you do not see it, go to step 4.
4. Type in your latitude, longitude (be sure to put a minus sign in front of the longitude entry), and GMT to local time conversion.
5. Select NEXT PASS. The applet will compute if there is a viewing opportunity for you. If the reentry is visible, you will then see something like the following figure displayed.
Fig. 8. Example of output screen from Skywatch program
To print the detailed table of predictions, click the PRINT button and you will get an output like in the following figure which might have been the trajectory as seen from San Jose, Costa Rica on STS-114 had the reentry actually occurred at the planned date/time. KSC217 is the name given to the 217th Shuttle orbit which was targeted to land at KSC.
Fig. 9. Example of hard copy from Skywatch program
Most of this information can easily be interpreted except for the columns labeled SRSS, SOLAR ALT, and SOLAR SEP. SRSS is a very important parameter and is the sun elevation. If that value is less than -11 degrees (that is, -15, -30 or some other value) the sky is dark. If the value is positive, the sun is above the horizon. It might even be possible to see the reentry even if the value is +3 to +5 provided the sun is hidden behind cloud in the east and the Shuttle is in the opposite part of the sky (and that part of the sky is clear). Ignore the columns labeled SOLAR ALT and SOLAR SEP since this information is not useful.
If you get the message NO ENTRY SIGHTING IS AVAILABLE FROM THIS LOCATION, it means you should try another city in the region to where you might have to travel. Otherwise, wait for another landing opportunity to be announced (if that occurs). Check the TV station CNN or the URL http://cnn.com for the latest information on Shuttle landing.
A sky chart feature is available. In Fig. 8 click on the SKY TRACK button and you can see a graphic of the path of the Shuttle against a star background (fig. 10).
Fig. 10. Path of Shuttle fireball against a constellation background is shown by a series of dots connected by a line that begins just right of center.
In figure 10, the horizon is represented by a straight line which is tilted in this figure and goes from the bottom center to upper right. You will have to orient the horizon to where that line is flat. Use the four buttons in the upper left part of the screen to control the tilt of the horizon line. Place the mouse cursor on one button and hold it down a few seconds until you get the feel for how to control the figure orientation. There is only one way to print the graphic. Push down both the ALT key and PRINT SCREEN at the same time and it will copy the figure onto your PC clipboard. Then use an application like Microsoft Power Point and paste the figure before printing it.
On the first return-to-flight mission of the Shuttle, STS-114 in August 2005, the first two proposed landing tracks are shown in the following diagram, with 1 being the prime opportunity and 2 being the next orbit.
Fig. 11. Ground tracks for aborted first two KSC opportunities during the STS-114 mission.
F. COMPLICATING FACTORS
Any phenomenon this beautiful and amazing cannot always be predicted with certainty far in advance. The main complicating factor is the weather conditions at the landing site. The reentry can be delayed or canceled without advance warning. Since communications are not that real-time, it is not possible to know when the delay or cancellation will occur. Also, notification of the exact track and viewing times may not be known until 24-48 hours before landing. Even after that, it is still possible to have a delay, cancellation or shift in the landing site away from Florida to another location. Check the web page in section E very frequently beginning 48 hours before landing and even as close to 30 minutes before the deorbit burn is scheduled for any updates.
Patience must be exercised. If you do not see the Shuttle on one opportunity, chances are it will not be visible from your area. Each day the predicted ground tracks have a tendency to move westward and NASA will likely want to bring the Shuttle home as soon as possible. Wait until the next mission.
G. RELATIONSHIP BETWEEN ELEVATION AND HORIZONTAL SLANT RANGE
The graph below shows various possible angles above the horizon for a reentry. The smaller the angle, the farther away the ground track. The importance of having an unobstructed horizon is fairly obvious. In general the Shuttle will be about 38 miles above Central America as it heads toward KSC traveling about 16 times the speed of sound. This is defined as Mach 16. The relationship between elevation and horizontal slant range (that is, distance from you to the point directly beneath the ground track[distance ‘D’ in the next figure]) is as follows:
Elevation is measured from the horizon (0 degrees elevation) to the overhead point (90 degrees elevation). The lower the elevation angle, the more chances of having some features obstruct the view of the reentry. Hence it is most imporant to consider potential good sites well in advance to plan reentry observation.
Fig. 12. Elevation of the Space Shuttle as seen by an observer at point A above the horizon. The distance from the observer along the ground to the point directly under the Shuttle flight path is the distance D.
Elevation 15 degrees, horizontal slant range (D) distance 142 miles
Elevation 30 degrees, distance D=66 miles
Elevation 45 degrees, distance D=38 miles
Elevation 60 degrees, distance D=22 miles
Elevation 75 degrees, distance D=11 miles
Elevation 90 degrees, distance D=0 miles
H. HOW LONG DOES IT TAKE BEFORE YOU CAN HEAR THE SONIC BOOM?
The above relationship implies that observers even at very long distances from the ground track, can spot the reentry assuming the sky is clear and there are no obstructions in between! Since the speed of sound through air is about 1100 feet per second, it will take any sonic boom a considerable period of time to propagate from the reentry altitude down to the ground. If the Shuttle passes precisely overhead (elevation 90 degrees) the propagation time is about 181 seonds (3 minutes). Using the above examples, the time to hear the sonic boom is as follows:
Elevation 15 degrees = 11.5 minutes
Elevation 30 degrees = 6.0 minutes
Elevation 45 degrees = 4.25 minutes
Elevation 60 degrees = 3.47 minutes
Elevation 75 degrees = 3.1 minutes
Elevation 90 degrees = 3.0 minutes
However, these times are approximate. Depending on wind speeds, wind direction and the presence of any background noise, you may or may not be able to hear the boom.
I. REENTRY TIMELINE
……..TWO DAYS BEFORE
Consult the reentry prediction URL to determine KSC landing opportunities as described in section E. Keep checking this site every few hours for updates up to the time of the first entry prediction in case changes have occurred.
……..ONE DAY BEFORE
1. Tape Recorder: The tape recorder must have a new tape rewound to the beginning of the tape; use fresh batteries to assure proper recording.
2. Camera and tripod: Be sure a cable release is attached if you want to take a time exposure. Check that the camera is securely mounted and that the focal length of the camera lens is no greater than 50mm.
3. Camcorder and tripod: Be sure you have a new recording medium in the camcorder (new tape or CD or DVD) and that the batter has been fully charged. It also helps to have a back up battery that is also fully charged.
4. Time signal receiver: The radio should be portable and have fresh batteries installed. 5. Digital watch with quartz accuracy (not mandatory but very useful; if you have a standard sweep second hand that is OK): be sure whatever type of watch that you use is synchronized to the time signal receiver so it is set as near as possible to the exact time.
6. Chair or mat: arrange to sit in a comfortable chair to make your observation or use a small pillow on a mat. Pay close attention to the use of a chair in the TRACKING section below.
7. Binoculars or telescope: Be sure your viewing device is securely mounted and can be tracked easily by hand without falling over or slipping away. It is recommended that you do not hand hold binoculars (unless the maximum elevation is expected to be quite high), but have them fixed to a tripod or similar device. If using a telescope be sure it has smooth elevation and azimuth control; use an eyepiece with the widest possible field of view.
8. Flashlight: preferably use one that is covered with red cellophane but this is not mandatory.
9. Compass: if you are not familiar with the constellations, use a compass in order to confirm the direction in which you will be looking.
10. Avoid distractions: do not invite a lot of people to observe with you as there may be a lot of noise created and this could cause problems with your own observation.
This section applies to whether you are using binoculars to observe the reentry or a camcorder to video tape it. Pay very close attention. If using binoculars, much will depend on the path that the Shuttle follows in the sky as to how you can smoothly track without interruption. For example, if the Shuttle only reaches a maximum elevation of 15 degrees, you will not have much difficulty to move your chair and binoculars from the start of the pass to the end. But if it passes at higher maximum elevations be prepared to change your body position; consider to sit on a small pillow on a mat. This could result in loss of tracking if you do not prepare properly ahead of time. One reason why NASA is so effective at flying space missions is that they train the crew extensively. Simulation is everything.
You can simulate several types of flight paths pretending to track the Shuttle with paths having a maximum elevation of 15, 45 and 90 degrees. Once you understand how to move your optics and body in conjunction with the change in angles, you can properly prepare the best combination of sitting position and tracking motions.
In the next figure there are three sample flight paths with a view from space down to the observer who is located at the point marked by the letter Z. The observer’s horizon is defined by the circle where N=North, W=West, etc. For the first case flight path 1 has the Shuttle rising in the west, reaching a maximum elevation of 15 degrees above the westnorthwest and then setting in the northwest. The change in azimuth is only about 60 degrees. In flight path 2 maximum elevation occurs around 45 degrees and the azimuth change is about 120 degrees. For case 3, the path is directly overhead and Shuttle flies west to east where maximum elevation is 90 degrees above the north. The Shuttle path can be oriented at any number of angles and these are just some of the possibilities.
Fig. 13. Sample flight paths that the Shuttle might take in the sky. Observer is located at Z.
In the following image, you can see a pair of binoculars secured to the top of a tripod using tie wraps. The binoculars can be secured with rope, tape or other material. The tripod head must be free to swivel in elevation and in azimuth; The eyepieces must fit comfortably in your eye socket(s) as you watch. The observer is seated on a small stool that has no back. This allows the observer to swivel 360 degrees without having to move the chair. The typical photographic tripod has both an elevation and azimuth lever which allows free movement and also for locking of each axis. It is best to loosen both locks when tracking. The next few images are for flight paths 1 and 2 as shown in figure 13.
Fig. 14. Binoculars on tripod.
Fig. 15. Observer looking west on rotating stool without a seat back.
Fig. 16. Observer looking northeast on the rotating stool.
The tripod can be positioned so that its legs are very close to the observer. It is possible that the observer may have to use both hands to control the tripod and binoculars. The tape recorder must be either operated by another person (held close to the observer’s mouth) or hung around the observer’s neck so the observer never has to actually handle it. Depending upon the height of the chair above the ground and the ability to extend the tripod legs, the observer should consider to allow the tripod to cover his/her legs.
Fig. 17. Tripod covering the observer’s legs.
A worst case scenario is where the observer has the misfortune (or good luck) to be located directly under the Shuttle flight path. See flight path 3 in figure 13. This presents the most awkward situation. One way to cope is to sit on a small pillow hand-holding binoculars for the whole pass. Keeping the binoculars on a tripod is not feasible. You must track the Shuttle from the rise point to the overhead point while also moving your body in azimuth to follow/anticipate the flight trajectory as it passes overhead. At this point the observer shift’s his/her body on the pillow to move a full 180 degrees. For such a difficult orientation there may be no way other than to hand-hold the binoculars during the entire episode, as uncomfortable as this may sound. It may be very useful to have a number of pillows or other items to place behind you and to the side to be used to support your head and arms.
Fig. 18A. Observer sitting on pillow facing the rise direction.
Fig. 18B. Observer sitting on pillow facing the overhead point.
Fig. 18C. Observer sitting on pillow facing the setting direction.
Since observer comfort is important, consider the flight path once it is known from your planned site and also draw a diagram like the one in figure 13 to show the change in elevation and azimuth from beginning to end. Then decide whether to use back support, arm support, head suport, mat, hard back chair, soft back chair or swivel chair (depending on what is available). You can see why being innovative can be of great use in overcoming obstacles.
Videotaping requires the same level of practice and sensitivity to the change in geometry of the flight path and your ability to maneuver through large angle changes described above.
Use of a telescope makes things difficult because you cannot move the whole telescope mounting itself during the tracking process to accommodate your body. You must move both your body and chair you are sitting on or you will lose the Shuttle. Another way is sit on a mat and not use a chair. In the photos that follow the observer sits on the mat tracking the Shuttle until it begins to get to a moderate elevation (say, 40 degrees) where the observer must start shifting position on the mat while tracking. This motion must be smooth because changes are occuring in both elevation and azimuth. The observer moves his/her body to the left anticipating Shuttle motion. The mat is oriented parallel to the flight path. As the Shuttle flies past the point of maximum elevation the swing in azimuth and drop in elevation causes the observer to have to shift body position again. The time signal radio must not be moved during this or any body position change and yet you must still be able to record the time signals and your voice.
The mat method will also work for moderate elevation passes with tripod-mounted binoculars and for tripod- mounted camcorders.
……..1 HOUR BEFORE FLYOVER
Do not keep photo or optical equipment in an air conditioned environment in the hour prior to the reentry. Check binoculars, telescope, camcorder equipment outside to be sure the lenses are not fogged. If lenses are fogged and there is not enough time for it to defog naturally, blast hot air from a hair dryer or other heat source on the lens surface to dissipate it. Find sample stars in any part of the sky whose magnitudes are known at +2, +3, +4, +5, +6, +7 and view them in your optical instrument so you can make comparisons to any object seen that might appear in the wake of the Shuttle fireball. (Camcorder users do not need to perform this step) If you do not have the capability to make such brightness estimates, you can opt not do do this comparison. The main thing is to be able to identify the appearance of any fragment and hopefully to estimate its brightness. Remember that the principal data you are after include the precise time an object or objects separate(s) from the fireball and the brightness of any and all such objects.
……..30 MINUTES BEFORE FLYOVER:
CHOOSE A SITE: Verify you have a good location with clear visibility of as much of the expected path through the sky as possible. The site should be free of lights except for your own flashlight.
Have all equipment outside and ready to go. Get familiar with the sky so you know for certain which direction is north, south, east, west.
If clouds are approaching and there is no time to move your location, stay put and observe anyway, even if the sky is nearly overcast.
……..5 MINUTES BEFORE FLYOVER
Allow your eyes to become dark-adapted. Keep all your equipment very close together but not so close that any wires might get tangled. Test your equipment now. Turn on the time signal receiver so that the volume is clear enough to be heard and recorded; be sure your tape recorder is close to the radio (camcorder) and your mouth so both the time signals and your voice are evenly recorded. If you are unsure, run a quick test recording your voice and time signals, and then play it back to check the volume levels. Adjust volume or placement of equipment as needed. Repeat the test as many times as it takes until both voice and time signals are clearly heard. Turn off after the test is completed.
If you are using a radio that is not portable and it is located inside a building or house, be prepared to start the camcorder or tape recorder 5 minutes before the reentry; record two full minutes of time signals and keep the device recording until after the Shuttle has passed. Do not turn off the camcorder or tape recorder until you have returned to the radio and recorded at least 2 full additional minutes of time signals after the Shuttle has disappeared. Don’t worry that the camcorder or tape recorder is not recording anything useful for a couple of minutes. It is possible that your radio may fail to receive signals at some point during your recording process. As long as you are recording continually and have at least two minutes of time on the front end and back end of your record this should be sufficient to establish an accurate time base across the observation period.
Begin looking for a bright object toward the horizon in the direction from which you expect the shuttle to appear. If you are using binoculars or a telescope, do not use them until you are sure you have the shuttle sighted visually. The fireball will be bright with a ‘contrail-like’ feature following behind it.
If you have a camcorder, be sure it is set to manual focus mode and find several stars of different magnitude to be sure they are in focus. Then turn OFF the camcorder to conserve battery power. The field of view of the lens should be set to about 2 degrees in width (or about four moon diameters).
……..2 MINUTES BEFORE FLYOVER
Turn on the radio time signals. Start tape recorder and begin to record the signals. If using a camcorder, do not active this device until you spot the Shuttle! Once you are positive you have the shuttle in sight, begin continuous recording and tracking in binoculars, camcorder, or telescope. Be sure the camcorder is on and in the RECORD mode and that it is clearly in focus. DO NOT ZOOM the camcorder IN and OUT. Keep it on one setting (see figure 6). Track the Shuttle with a smooth motion keeping the fireball either in the center or between the center and the leading edge of the frame.
Watch the fireball closely and continuously and call out if you see any piece of debris that comes off. Keep watching until you lose sight of the shuttle permanently. Remember, even if you do not see any debris pieces this is a good data point to report and we want to know about it.Keep your recording equipment running ONLY if you want to try to record the sonic boom(s) which will take some minutes to be audible (if at all).
………12 MINUTES AFTER FLYOVER
By now the sonic boom(s) should have been heard. You can estimate the time it takes for sound to propagate through the air to reach you from the preceding information. This time would be earlier if the shuttle passed higher than 15 degrees above the horizon at closest approach. If you have not already done so, turn off all equipment.
J. DO YOU WANT TO JOIN CARON?
Please send me an email (firstname.lastname@example.org) and let me know your name, location, and planned method of observation.
K. HOW TO REPORT YOUR OBSERVATIONS
If you have tracked the shuttle in binoculars or telescope or camcorder and observed it continuously or partially for certain period(s), contact email@example.com first to let me know what you have recorded. Instructions will then follow if we need to hear your audio tape or see any camcorder images. However, please complete the following form and attach it to an email.
CARON REPORT FORM 9/28/05
(PLEASE PRINT OR TYPE ANSWERS TO ALL QUESTIONS IN ENGLISH)
(SEND TO firstname.lastname@example.org AFTER THE REENTRY only if you made observations)
BEFORE COMPLETING THIS FORM, BE SURE YOU ARE REPORTING THE SPACE SHUTTLE AND NOT AN AIRPLANE, METEOR OR OTHER ARTIFICIAL EARTH SATELLITE. PLEASE THEN ANSWER EACH QUESTION EXACTLY.
1. COMPLETE NAME OF PERSON REPORTING THE OBSERVATION
1B. GENDER (MALE OR FEMALE)
1C. CLOSEST TOWN OR CITY TO YOUR OBSERVATION SITE
2. EMAIL ADDRESS
3. COMPLETE POSTAL ADDRESS
4.TELEPHONE NUMBER (HOME, WORK, CELL PHONE)
5. WHAT EQUIPMENT WAS USED TO MAKE THE OBSERVATION (E.G. NAKED EYE, BINOCULAR, TELESCOPE, CAMCORDER, CAMERA, OTHER)
6. IF A CAMCORDER WAS USED, WHAT MAKE, MODEL, VIDEO CASSETTE TYPE, CAMCORDER LENS, TYPE OF RECORDING MEDIUM (E.G. DIGITAL, 8MM)?
6A. DID YOU ZOOM THE CAMCORDER LENS?
6B. DID YOU USE AUTO FOCUS OR MANUAL FOCUS?
7.SPECIFY HOW THE RECORDING DEVICE (CAMERA/CAMCORDER) WAS MOUNTED.
8. IF A TIME EXPOSURE PHOTO WAS MADE, WHAT WAS THE LENGTH OF EACH EXPOSURE, TYPE OF FILM, TYPE OF CAMERA, CAMERA LENS?
9.IF AN EXACT TIME SIGNAL SOURCE WAS USED, WHAT WAS THAT SOURCE (RADIO AND FREQUENCY?)
10.WHERE WAS THE OBSERVATION MADE? SPECIFY LATITUDE AND LONGITUDE IN DEGREES, MINUTES AND SECONDS. ALSO ELEVATION OF THE SITE IN FEET OR METERS. PREFERABLY USE A GPS RECEIVER OR TOPOGRAPHIC MAP.
11. IF YOU DO NOT HAVE A GPS, HOW DID YOU DETERMINE YOUR EXACT LATITUDE/LONGITUDE?
12.DATE (DAY, MONTH, YEAR) AND TIME (EITHER LOCAL OR UNIVERSAL OR GMT) TIME (HOURS, MINUTES, SECONDS) OF YOUR OBSERVATION PERIOD
13. DIRECTION YOU WERE FACING WHEN YOU FIRST SAW THE SHUTTLE (NORTH, SOUTH, EAST OR WEST) AND DIRECTION WHEN IT DISAPPEARED FROM VIEW.
14. NAMES OF OTHER PEOPLE WITH YOU WHO ALSO MADE DETAILED OBSERVATION (IF ANY) THAT WOULD BE INDEPENDENT FROM YOURS.
15. WAS YOUR TRACKING CONTINUOUS OR DID YOU TAKE BREAKS?
16. DID YOU TALK INTO A TAPE RECORDER TO RECORD THE ENTIRE EXPERIENCE? IF SO, WHAT WAS THE MODEL AND TYPE OF TAPE (E.G. 8MM).
16A. IF YOU DOCUMENTED TIME SIGNALS AND THE APPEARANCE OF DEBRIS SHED FROM THE SHUTTLE ON YOUR TAPE RECORDER, PLEASE PROVIDE THE EXACT TIMES AND DESCRIPTIONS OF EACH EVENT. (E.G. AT 09HRS 42MIN 12SEC UNIVERSAL TIME, A SMALL PIECE APPEARED FROM THE BACK OF THE FIREBALL AND THEN DISAPPEARED AFTER A FEW SECONDS)
17. WHAT DID YOU SEE THAT WAS UNUSUAL? PLEASE DESCRIBE AND DRAW BEST DETAILED PICTURE ESPECIALLY IF YOU DID NOT PHOTGRAPH OR VIDEO RECORD.
18. IF YOUR OBSERVATION WAS NOT RECORDED PHOTOGRAPHICALLY AND YOU VISUALLY SAW ANY SMALL PIECE OR PIECES DETACH, INDICATE THE TIME WHEN YOU SAW EACH ONE (HOURS, MINUTES, SECONDS GMT OR LOCAL TIME).
19. IF YOU HAVE EXPERIENCE ESTIMATING ASTRONOMICAL BRIGHTNESS (MAGNITUDES), ESTIMATE THE BRIGHTNESS OF EACH PIECE THAT WAS SEEN.
20. DID YOU HEAR ANY SOUNDS SUCH AS A LOUD BOOM(S)? IF SO, WAS IT RECORDED ON TAPE? WHAT TIME(S) DID IT/THEY OCCUR?
21. DESCRIBE THE WEATHER, TEMPERATURE, SKY CONDITIONS, INTERFERENCE OF CLOUDS OR STREET LIGHTS OR OBSTRUCTIONS THAT IMPEDED YOUR ABILITY TO TRACK THE SHUTTLE CONTINUOUSLY.
22. DESCRIBE ANYTHING MEMORABLE ABOUT THIS EXPERIENCE THAT WAS NOT DESCRIBED IN YOUR ANSWERS TO THE PRECEDING QUESTIONS.
23. ARE YOU ABSOLUTELY POSITIVE THAT YOUR OBSERVATION WAS NOT OF AN AIRPLANE, ANOTHER ARTIFICIAL SATELLITE OR METEOR?
24. DESCRIBE ANY PREVIOUS OBSERVATIONAL EXPERIENCE THAT INDICATES YOUR KNOWLEDGE OF THE NIGHT SKY, CONSTELLATIONS, ASTRONOMY, EDUCATIONAL BACKGROUND.
Thank you for your report!