Transit 3B
Encyclopedia
Transit 3B was an American
satellite which was launched in 1961 and operated by the United States Navy
. It was a replacement for Transit 3A, which was lost in a launch failure the previous year. It carried instruments to demonstrate navigation and timing systems, and study geodesy
to support the development of the Transit
satellite navigation system.
The launch of Transit 3B was conducted at 03:45 UTC on 22 February 1961, using a Thor DM-21 Ablestar
rocket flying from Launch Complex 17B at the Cape Canaveral Air Force Station
. The LOFTI-1
satellite was launched aboard the same rocket. The rocket and upper stage used had the serial numbers Thor 313 and Ablestar 007 respectively. The launch resulted in a partial failure, with the spacecraft being placed in a more eccentric
orbit than planned, and failing to separate from the upper stage.
Transit 3B was a 113 kilograms (249.1 lb) spacecraft, which was powered by 6,600 solar cells charging a nickel-cadmium battery
. It ended up in a low Earth orbit
with a perigee
of 167 kilometres (103.8 mi), an apogee
of 1002 kilometres (622.6 mi), and 28.3 degrees of inclination
. It had an orbital period
of 96.4 minutes. Due to the low perigee of its orbit, Transit 3B decayed
quickly, and reentered
the atmosphere on 30 March 1961, less than 37 days after launch. Despite being in the wrong orbit and operating for less time than had been planned, some useful data was returned from the mission.
The systems demonstrated by Transit 3B included a digital clock to control timing signals, uploading programs into the onboard computer's memory whilst in orbit, data retention and FM encoding, and the use of phase modulation
for data transmission without affecting the satellite's Doppler signal. The satellite's computer had a memory capacity of 48 bytes.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
satellite which was launched in 1961 and operated by the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
. It was a replacement for Transit 3A, which was lost in a launch failure the previous year. It carried instruments to demonstrate navigation and timing systems, and study geodesy
Geodesy
Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...
to support the development of the Transit
Transit (satellite)
The TRANSIT system, also known as NAVSAT , was the first satellite navigation system to be used operationally. The system was primarily used by the U.S...
satellite navigation system.
The launch of Transit 3B was conducted at 03:45 UTC on 22 February 1961, using a Thor DM-21 Ablestar
Thor-Ablestar
The Thor-Ablestar, or Thor Able-Star, also known as Thor-Epsilon was an American expendable launch system consisting of a PGM-17 Thor missile, with an Ablestar upper stage...
rocket flying from Launch Complex 17B at the Cape Canaveral Air Force Station
Cape Canaveral Air Force Station
Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...
. The LOFTI-1
LOFTI-1
LOFTI-1 was an American satellite which was launched in 1961 and operated by the United States Navy and Naval Research Laboratory. It was used to conduct research into the propagation of very low frequency radio signals in the ionosphere, and to investigate if these signals could be received by...
satellite was launched aboard the same rocket. The rocket and upper stage used had the serial numbers Thor 313 and Ablestar 007 respectively. The launch resulted in a partial failure, with the spacecraft being placed in a more eccentric
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
orbit than planned, and failing to separate from the upper stage.
Transit 3B was a 113 kilograms (249.1 lb) spacecraft, which was powered by 6,600 solar cells charging a nickel-cadmium battery
Nickel-cadmium battery
The nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....
. It ended up in a low Earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
with a perigee
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
of 167 kilometres (103.8 mi), an apogee
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
of 1002 kilometres (622.6 mi), and 28.3 degrees of inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
. It had an orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
of 96.4 minutes. Due to the low perigee of its orbit, Transit 3B decayed
Orbital decay
Orbital decay is the process of prolonged reduction in the altitude of a satellite's orbit.This can be due to drag produced by an atmosphere due to frequent collisions between the satellite and surrounding air molecules. The drag experienced by the object is larger in the case of increased solar...
quickly, and reentered
Atmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
the atmosphere on 30 March 1961, less than 37 days after launch. Despite being in the wrong orbit and operating for less time than had been planned, some useful data was returned from the mission.
The systems demonstrated by Transit 3B included a digital clock to control timing signals, uploading programs into the onboard computer's memory whilst in orbit, data retention and FM encoding, and the use of phase modulation
Phase modulation
Phase modulation is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave.Unlike its more popular counterpart, frequency modulation , PM is not very widely used for radio transmissions...
for data transmission without affecting the satellite's Doppler signal. The satellite's computer had a memory capacity of 48 bytes.