By Steven J. Stromer
One of the many limitations we come up against in urban skywatching is the inability to see to the horizon. At best, the first and last twenty degrees of an object's trajectory are obscured by buildings, resulting in a significantly smaller viewing window. One way to minimize this loss is to know precisely where to be looking when an object comes into view.
Today, we are going to focus, not on predicting the rise and set of celestial objects, but rockets. NASA's Anomalous Transport Rocket Experiment (ATREX) calls for five rockets to launch in quick succession from NASA's Wallops Flight Facility, located near the coast of Virginia. The rockets will intentionally reach into the upper atmosphere, where they will almost simultaneously release payloads of trimethyl aluminum, creating highly visible, white clouds. Researchers will observe the movements of these clouds with the hope of better understanding high-altitude, high-speed jet stream behavior.
What you will see
Both the rockets' trails and their chemical clouds will be visible to observers in New York. The rockets should become viewable on the New York horizon at approximately two minutes into their flight. This unavoidable loss of observing time, caused by the slight curvature of the Earth between Virginia and New York, can be more positively viewed as offering New York observers brief forewarning to ready their cameras, binoculars and telescopes.
Each rocket will follow an eastward trajectory with a differing payload release distance from the launch facility (see image, top right). Together, the man-made clouds will produce a latitudinal line spanning hundreds of miles out into the Atlantic Ocean. The clouds are then expected to dissipate within about twenty minutes.
Calculate the direction in which to watch
1. To obtain precise latitude and longitude coordinates for both the observer's position and launch position use Google Maps. In my example, I will be observing from Brooklyn's Prospect Park:
Prospect Park, Long Meadow position:
40.668693, -73.970697
+40° 40' 7.29", -73° 58' 14.51"
Wallops Flight Facility, Virginia position:
37.941490, -75.466554
+37° 56' 29.36", -75° 27' 59.59"
2. Visit:
http://www.movable-type.co.uk/scripts/latlong.html
and enter the latitude and longitude coordinates for both observer's position and launch position into the haversine formula calculator at the top of the page.
The calculator accepts coordinates in the following formats:
deg-min-sec suffixed with N/S/E/W
(e.g. 40°44'55"N, 73 59 11W)
or, signed decimal degrees without compass direction
(e.g. 40.7486, -73.9864 Note: negative indicates west/south)
The calculator will return results much like this:
Distance: 204.6 miles (329.4 km)
Initial bearing: 203°28'27"
Final bearing: 202°31'35"
(see image, center right)
Note: Due to the relatively short distance between points, the initial and final bearings are very close. For our purposes, 202-203° is sufficiently accurate; the rockets will likely be highly visible, and will be quickly moving away from this bearing, anyway.
3. Project the angle onto a local map, as illustrated at right. The bearing represents the number of degrees to measure from North. To accurately locate this angle in the physical world, use a compass. If you do not already own one, download a compass app for your smartphone (many are free).
You now have an approximate angle for viewing the ATREX rockets and experiment. Now, all we need is a break in the clouds and fog for the launch to be conducted and enjoyed!
For practice, try calculating the degree angle for the five rockets' expected splashdown locations:
Splashdown #1 (closest to shore):
37.6890758, -74.5823578
Splashdown #2:
37.6199731, -74.1744435
Splashdown #3:
37.252432, -72.1082004
Splashdown #4:
36.9973835, -70.9128751
Splashdown #5 (furthest from shore):
36.517987, -68.7797165
For coordinates along the full flight trajectories of the ATREX sounding rockets,
download this Google Earth .kmz file from NASA.
Keep track of activities, and join us at future events.
Source: http://www.nasa.gov/mission_pages/sunearth/missions/atrex.html
