Weather satellites and their photos were invaluable to the bombing missions of the U.S. Navy and Air Force in Southeast Asia. In a CBS television interview in the late 1960s, General William Momyer, commander of the air war, stated that meteorological satellite use in Southeast Asia operations was among the most significant innovations of the air war.
The need for a nearly cloud-free environment was never so much a premium as in the air war in Vietnam. Precision bombing in the north meant that Navy and Air Force fighter-bombers had to acquire their targets visually from an altitude of 15,000 feet, yet North Vietnam was almost always covered by clouds.
The weather-reporting network in Southeast Asia was sparse, at best. The United States was denied use of any weather-reporting station of the enemy because the enemy falsified observations, failed to report at all, or if so, coded the data. U.S. meteorologists did debrief fighter and bomber pilots, and they gleaned data from special reconnaissance flights. But both of these methods untrustworthy because the observation were obtained under duress; the pilots were subjected to enemy aircraft fire ground fire, and surface-to-air missile—and sometimes all three. In addition, the often erratic monsoon seasons exacerbated the meteorologist’s forecasting problems. Meteorological satellite imagery, therefore, was the primary observational and short-term forecast tool.
I arrived in Saigon in 1966, assigned to forecast weather for the 377th Bomb Wing missions that bombed North Vietnam, Laos, and northern South Vietnam. At that time, the American public was not aware that North Vietnam was being bombed from Thailand, not from South Vietnam. The bombers took off from four Air Force bases in Thailand: Khorat, Ubon, Udorn, and Tahkli. The refueling was done by the Strategic Air Command (SAC) out of Satahib Air Force Base south of Bangkok.
Weather Satellites and Their Photos: During the Vietnam War, meteorological satellite use in Southeast Asia was vital to United States as well as Army of the Republic of Vietnam (ARVN) operations, although little publicity was given this space-age product. The dissemination of the imagery naturally was restricted, although meteorological information derived from the photos was relayed throughout Southeast Asia via the tele-communications network for operational use.
Weather satellite data used in early Southeast Asia operations were acquired at Tan Son Nhut Air Force Base (Site VI), South Vietnam, and Udorn Air Force Base (Site VIII), Thailand. The U.S. Navy also had satellite readouts on hoard some of its aircraft carriers. Unfortunately, in much of the early Southeast Asia action the Navy lagged the Air Force in satellite read-out equipment installation and tracking. This situation was remedied completely by 1970. The USS Constellation (CVA-64) was the first aircraft carrier to have shipboard Defuse Meteorological Satellite Program (DMSP) readout.
Evidence indicated that the Chinese and possibly the North Vietnamese also were processing daytime satellite photos, sometimes, intercepted surface observations reported bad weather when the satellite photos indicated just the opposite. My weather commander commented that this falsification of meteorological information was a violation of the World Metrological Organization Code.
“What would you do if you were bombed on clear days only?” I replied.
A variety of meteorological satellites "'as used in the mid- and late-1960s, as well as the early 1970s. These vehicles were sponsored by the U.S. Weather Bureau (now the National Oceanic and Atmospheric Administration [NOAA], NASA, and the Department of Defense. Anyone who had VHF receiving equipment could use the U.S. Weather Bureau and NASA satellites, which had automatic picture transmission.
These Environmental Science Services Administration (ESSA) and Nimbus (Latin for rain cloud) satellites were sun synchronous, which means they took photos at nearly the same location and at the same time each day. ESSA information was available from 0700 to 0900, and Nimbus from 1100 to 1300. In addition, a weather bureau satellite that taped stored imagery on the spacecraft and processed data for the entire world to Washington, D.C., was programmed just for the war effort to transmit signals that could be processed only on encrypted DoD photo processors. These afternoon birds (1500-1700) were given the code name Nat and provided superb information via the sun-synchronous spacecraft.
DoD had its own command-and- control meteorological satellites. The sun-synchronous satellites, orbiting at 450 nautical miles, produced day and night visual and infrared imagery around 0700, 1200, 1900, and 0000—all local times. This program grew out of a need for the military to have the best weather information available around the world and started in the early 1960s in the space systems division of Air Force Systems Command in Los Angeles. It still exists.
Data from these satellites were invaluable because of the weather patterns in the area. Satellite meteorologists coined the expression “wind sock” to describe the cloud patterns in North Vietnam’s panhandle. The moisture from the South China Sea seemed to be sucked into the Mekong River delta, causing widespread low cloud cover over the area most of the time. Locating geographical features in the North, especially searching for holes through which our fighter-bombers could penetrate toward their targets, could, therefore, be difficult because of this widespread cloud cover. Satellite meteorologists devised an analysis scheme to use the early-morning strati as grid markers, since these low clouds filled the river valleys. A contemporary of mine. Bob Fett, discovered this technique and it became one of the most useful features for satellite meteorologists to grid and locate targets over the north.
The sun’s heat dissipated these stratus clouds, so by noon they gave way to fair- weather cumulus clouds along the ridge mountain lines. On some rare clear days, important landmarks such as Thud Ridge, the Red River Valley, or even the Red River Delta could easily be seen. F-105 and F-4 fighter bombers often made their way down Thud Ridge or on either side of it to targets in the panhandle of North Vietnam.
We also could detect cloud coverage and wind flow on many of these photos. The high-resolution imagery made it easy to determine geographical landmarks for accurate gridding through Southeast Asia. The Vietnam coastline itself provided significant features for marking each latitude. These geographical markings enabled real-time satellite imagery to be gridded instantaneously. These gridded, analyzed photos were used for many Southeast Asia missions.
Nighttime low-light visual data from the DoD satellites added another bonus for Southeast Asia operations after 1969. At night, a full moon illuminates tropical storms and thunderstorm clouds. Of course, the simultaneous infrared pictures that went with the visual data could easily be gridded by using city-light location that was visible all over Asia. Fires of all kinds, especially the man-made rice paddy variety, also showed up on these night photos. These fires, used to clear the rice fields before replanting, generated widespread smoke and haze that hampered visibility in the area. It was easy to track the movement and coverage of the smoke. Smoke was sometimes carried aloft to 30,000 feet or higher and its monitoring by satellite images was important to all kinds of DoD and ARVN operations.
Applications of Satellite Information: Just northwest of Hanoi, on one of the bombing runs, was a narrow, tree- covered mountain ridge. On weather satellite photos one could easily see this dark area, which could be used to pinpoint the weather in the Hanoi bombing area. It was known as “Thud Ridge.”
According to some pilots with World War II and Korean War experience. Thud Ridge was the most heavily defended area ever put together. There were antiair missiles, radar-controlled guns, fighter planes, and random firing from ground troops; it was indeed a nightmare for bomber pilots. Many times I heard confused yelling over the intercom as pilots talked to each other on that dreaded trip from Khorat to be refueled before heading into the bowels of North Vietnam.
The designated area of North Vietnam to be bombed was called Route Pack 6-A and 6-B. When the targets were in Route Pack 6, the day was not going to be easy. As the chief weather officer, I was in charge of a group of young forecasters. I used to instruct them never to say that the weather was going to be perfect the next day in North Vietnam, because the pilots would not sleep well, knowing their mission was inevitable. I figured the least we owed them was a halfway decent night’s sleep.
The Thuds (F-105 fighter-bombers) and later the F-4s required air-to-air refueling on their way to the Northern targets from bases in Thailand. Occasionally, a Navy aircraft also needed fuel from Strategic Air Command KC-135s.
The tanker fleet that flew tracks over Southeast Asia depended heavily on a cloud and turbulence-free environment at the refueling altitude.
Gunship missions, strafing, napalming, and rescue missions also relied on good low-level weather. Modem air systems such as television bombs, laser devices, and other sophisticated electronic weapons could be hampered by intervening weather.
The Navy Strikes the Thanh Hoa Bridge: The Thanh Hoa Bridge spans the Song Ma River in North Vietnam and is located three miles north of the town of Thanh Hoa, the capital of the Annam Province. This bridge replaced the original French-built bridge, which the Viet Minh destroyed in 1945. The new bridge at Thanh Hoa was 550 feet long, 56 feet wide, and about 50 feet above the river. It had two steel through-truss spans that rested in the center of a massive reinforced concrete pier 16 feet in diameter and on concrete abutments at the ends. This giant bridge would prove to be one of the single, most challenging targets for U.S. air power.
On 17 June 1965, the U.S. Navy began a three-year effort to destroy this bridge. Primary Navy attack aircraft included A-4 Skyhawks, A-7 Corsair IIs, A-6 Intruders, F-4B Phantoms, and, on occasion, A-3B Sky Warriors and F-8 Crusaders. These planes delivered vast amounts of ordnance on the bridge in an effort to deny its use by North Vietnamese trains and trucks. Using visual as well as radar bombing techniques, the Navy had succeeded only in shaking the steel girders. The approaches to the bridge, however, were battered to the point where according to one Navy official, “The general area looked like the valley of the moon.”
The proximity of the Thanh Hoa Bridge to the Gulf of Tonkin—only 11 miles inland—together with the normal weather patterns over the northern part of North Vietnam, combined to provide low, poor weather over the target area much of the year. Low cloud ceilings, fog, smoke from burning fields, and a continual haze hampered Navy efforts to locate and destroy the bridge. In some seasons, poor weather permitted only two to four visual attacks per month. This, of course, worked to the enemy’s advantage, providing time to repair the bridge and thus keep lines of communication open.
Meteorological satellite data helped tell the target planners just when the weather would break. Improved day and night sensors made it effective in the late 1960s. Night visual cameras on board DoD’s satellite could pinpoint burning rice paddy fields and thus warn pilots of the extent of smoke or haze coverage. The satellite’s nighttime visual capability also was used extensively in locating a simultaneous thermal views of Southeast Asia that showed different cloud-top levels and breaks in clouds at nighttime.
Son Tay POW Raid: One of the most publicized operations in Southeast Asia was the attempt to rescue prisoners-of- war from Son Tay in 1970. Ideal weather occurred during that operation. When a typhoon or tropical storm approached the South China Sea from the east, the northeast low-level flow preceding the storm caused the weather to clear in North Vietnam. During the Son Tay raid, this storm movement permitted a highly accurate three-to-five day forecast.
U.S. Army Operations: The U.S. Army used intelligence gained from meteorological satellites for air as well as ground operations. Natural river flooding was particularly important to the Army in many areas of Southeast Asia. Early morning low-sun-angle views of the region enabled glints off of rivers and lakesto be enhanced on the photos if no clouds were present. The glint would show any other flooding areas. Naturally severe thunderstorms and heavy rainfall areas were also passed to Army ground forces. The illumination of the moon also help satellite interpretation.
The Mayaguez Incident: Well after the Vietnam War concluded, weather satellites played another part in Southeast Asia. When the Cambodians captured the U.S. merchant ship Mayaguez in May 1975, President Gerald R. Ford faced with a difficult decision. The ship was being kept off Koh Tang Island. The only surface observations came from Thailand. As always, the meteorological satellite was the most powerful weather observing tool. When the Marine stormed the island, tactical air refueling areas were moved on 14 May as the result of satellite photography from the site Nakhon Phanom in eastern Thailand Moreover, the decisions to recover some damaged helicopters on the Thai mainland rather than ditch in the sea were made possible because daily visual photographs verified that weather along the route was favorable.
Throughout the Vietnam War and even afterwards, the meteorologists and theirimagery proved their worth in supplying much-needed weather information in an area that was nearly devoid of the conventional weather stations that we enjoy here in the United States. In future conflicts, wherever they may be, weather satellites will once again be a prime source of information.