Vela 4B

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

{{Infobox spaceflight

| name = Vela 4B

| image = HD.6D.927 (10405785575).jpg

| image_alt =

| image_caption =

| mission_type =

| operator = USAF

| website =

| COSPAR_ID = 1967-040B{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1967-040B|title=Vela 4B|last=NASA Goddard Space Flight Center|access-date=28 September 2019}} {{PD-notice}}

| SATCAT = 2766{{cite web|url=https://in-the-sky.org/spacecraft.php?id=2766|title=OPS 6679|work=In-The-Sky.org|first=Dominic|last=Ford|access-date=28 September 2019}}

| mission_duration =

| spacecraft_bus =

| manufacturer = TRW

| dry_mass =

| launch_mass = {{convert|225|kg|lb}}

| power = 120 W

| launch_date = {{start-date|April 28, 1967, 10:01|timezone=yes}} UTC

| launch_rocket = Titan 3C-10

| launch_site = Cape Canaveral LC-41

| launch_contractor =

| entered_service =

| disposal_type =

| deactivated =

| orbit_epoch = 1 May 1967

| orbit_reference = Geocentric

| orbit_regime = Highly Elliptical

| orbit_periapsis = {{convert|107,337|km|mi}}

| orbit_apoapsis = {{convert|114,612|km|mi}}

| orbit_inclination = 33.06°

| orbit_semimajor =

| orbit_eccentricity =

| orbit_period = {{convert|6,671.8|minutes|hours}}

| apsis = gee

| programme = Vela

| previous_mission = Vela 4A

| next_mission = Vela 5A

}}

Vela 4B (also known Vela 8 and OPS 6679{{cite web|url=https://www.lib.cas.cz/space.40/1967/040B.HTM|title=1967-040B - Vela 8|work=Space 40|last=Antonín Vítek|access-date=28 September 2019}}) was an American reconnaissance satellite to detect explosions and nuclear tests on land and in space. It was released together with Vela 4A, ERS 18, OV5 1 and OV5 3.{{cite web|url=https://space.skyrocket.de/doc_sdat/vela_adv.htm|title=Vela 7, 8, 9, 10, 11, 12 (advanced Vela)|first=Gunter|last=Krebs|work=Gunter's Space Page|access-date=28 September 2019}}