Vela 2B

{{Short description|U.S. reconnaissance satellite}}

{{Infobox spaceflight

| name = Vela 2B

| image = Vela5b.jpg

| image_size = 180px

| image_caption = Vela satellite.

| mission_type =

| operator = USAF

| website =

| COSPAR_ID = 1964-040B{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-040B|title=Vela 2B|last=NASA Goddard Space Flight Center|access-date=July 28, 2019}} {{PD-notice}}

| SATCAT = 837

| mission_duration =

| spacecraft_bus =

| manufacturer = TRW

| dry_mass =

| launch_mass = {{convert|135|kg|lb}}

| power =

| launch_date = {{start-date|July 17, 1964, 08:22|timezone=yes}} UTC

| launch_rocket = Atlas LV-3A Agena-D

| launch_site = Cape Canaveral LC-13

| launch_contractor =

| entered_service =

| disposal_type =

| deactivated =

| orbit_epoch = {{start-date|July 17, 1964}}

| orbit_reference = Geocentric

| orbit_regime = Highly Elliptical

| orbit_periapsis = {{convert|94,436|km|mi}}

| orbit_apoapsis = {{convert|11,775|km|mi}}

| orbit_inclination = 40.8°

| orbit_semimajor =

| orbit_eccentricity =

| orbit_period = 100,12 hours

| apsis = gee

| programme = Vela

| previous_mission = Vela 2A

| next_mission = Vela 3A

}}

File:Atlas Agena D with Vela 2A, Vela 2B and ERS 13 (Jul. 17 1964).jpg

Vela 2B (also known Vela 4, Vela Hotel 4 and OPS 3674{{cite web|url=http://www.lib.cas.cz/www/space.40/1964/040A.HTM|title=1964-040B - Vela 3|work=Space 40|last=Antonín Vítek|access-date=July 28, 2019}}) was a U.S. reconnaissance satellite for detecting explosions and nuclear tests on land and in space, the first of the second pair of Vela series satellites, taken together with Vela 2A and ERS 13 satellites. The secondary task of the ship was space research (X-rays, gamma rays, neutrons, magnetic field and charged particles).

The satellite was rotationally stabilized (2 rps). The ship could work in real time mode (one data frame per second) or in data recording mode (one frame every 256 seconds). The first mode was used for the first 40% of the mission's duration. The second one was used until the next pair of Vela satellites were launched.

The ship remains in orbit around Earth.