The North American blizzard of 2008 was a winter storm that struck most of southern and eastern North America from March 6 to March 10, 2008.
 The storm was most notable for a major winter storm event from Arkansas to Quebec.
 It also produced severe weather across the east coast of the United States with heavy rain, damaging winds and tornadoes, causing locally significant damage.
 The hardest hit areas by the wintry weather were from the Ohio Valley to southern Quebec where up to a half a meter of snow fell locally including the major cities of Columbus, Ohio, Cleveland, Ohio, and Ottawa, Ontario.
 For many areas across portions of the central United States, Ontario and Quebec, it was the worst winter storm in the past several years.
 The blizzard and its aftermath caused at least 17 deaths across four US states and three Canadian provinces, while hundreds others were injured mostly in weather-related accidents and tornadoes.
A winter storm warning (SAME code: WSW) is a statement made by the National Weather Service of the United States which means a winter storm is occurring or is about to occur in the area, usually within 36 hours.
 Generally, a Winter Storm Warning is issued if the following criteria, at least, are forecast: usually between 4 in to 7 in or more of snow or usually 3 in or more of snow with a large accumulation of ice.
 In the Southern United States, where severe winter weather is much less common and any snow is a more significant event, warning criteria are lower, as low as 1 in in the southernmost areas.
 (Thus, as you go from south to north the necessary accumulations get higher.)
 A warning can also be issued during high impact events of lesser amounts, usually early or very late in the season when trees have leaves and damage can result.
 Winter Storm Warnings are issued when winds are less than 35mph; if the storm has winds above this wind speed, it becomes a blizzard warning.
Texas Tower 4 (ADC ID: TT-4) was a former United States Air Force Texas Tower General Surveillance Radar station, located 63 mi south-southwest off the coast of Long Island, New York in 185 ft of water.
 The tower was the site of a tragic accident and was destroyed by a winter storm on January 15, 1961.
 None of the twenty-eight airmen and civilian contractors who were manning the station survived.
The 858th Radar Squadron is an inactive United States Air Force unit.
 It was last assigned to the 26th Air Division, Aerospace Defense Command, stationed at Fallon Air Force Station (Naval Air Station Fallon), Nevada.
 It was inactivated on 30 June 1975.
The Puerto Rico Air National Guard (PR ANG) —Spanish: "Guardia Nacional Aérea de Puerto Rico" — is the air force militia of the Commonwealth of Puerto Rico, an unincorporated territory of the United States of America.
 It is, along with the Puerto Rico Army National Guard and the Puerto Rico State Guard, an element of the Puerto Rico National Guard.
 After beginning as four units, the PRANG expanded to 11 units by the 1980s, including the 1956th Tactics Combat Group, the 140th Radar Squadron and others.
The Early December 2007 North American winter storm was a major winter storm which affected the majority of the United States and portions of southern Canada from November 29 to December 5, hitting the Intermountain West and Midwestern United States, the Great Lakes region and the Northeast.
 The storm brought significant snows to portions of the Upper Midwest, Great Plains and Great Lakes regions of the United States and Canada on December 1 with a major winter storm for Quebec, Ontario and parts of the Northeast region on December 2 and 3 as well as the Canadian Maritimes on December 4 and 5.
 The system was also responsible for a major ice storm across the Midwestern states which caused disruptions to several major cities including Des Moines, Chicago, Detroit, Milwaukee and Toronto.
 The storm was blamed for at least 16 deaths across nine US states and one Canadian province.
 10 traffic deaths had been reported, as of 2 December 2007.
The Saskatchewan Blizzard of 2007 was a winter storm that struck northeastern British Columbia, central Alberta and central Saskatchewan on Wednesday, January 10, 2007.
 The storm hit the city of Saskatoon severely and is considered to be one of the worst storms in Saskatchewan's history.
 It brought motor vehicle traffic to a standstill, stranded people and shut down many public services.
 There were two fatalities from the storm.
The 635th Radar Squadron is an inactive United States Air Force unit.
 It was last assigned to the 20th Air Division, Aerospace Defense Command, stationed at Dauphin Island Air Force Station, Alabama.
 It was inactivated on 1 July 1974.
 The unit was a General Surveillance Radar squadron providing for the air defense of the United States.
Othello Air Force Station (ADC ID: P-40, NORAD ID: Z-40) is a closed United States Air Force General Surveillance Radar station.
 It is located 7.2 mi south of Othello, Washington.
 It was the home station of the 637th Aircraft Control and Warning Squadron (AC&W Sq) (later the 637th Radar Squadron) and the 637th Air Defense Group, closing in 1975.
The 646th Aircraft Control and Warning Squadron was the operational USAF unit of Highlands Air Force Station.
 The unit manned the Texas Tower 4, an offshore radar annex from 1958 until it collapsed into the Atlantic Ocean on January 15, 1961, killing 28 people.
 The squadron was activated on June 1, 1948, and renamed to the 646th Radar Squadron (SAGE) on Oct 1, 1958.

Question: When the winter storm hit Texas Tower 4, what was the 646th Radar Squadron's role?
Answer: unit manned