Virginia couples' median income, adjusted for inflation, rose 2.1 percent in 1984 following a 2.3 increase in 1983, the steepest two-year increase since records first were kept in 1972, according to a study by the University of Virginia.

"The 2.1 percent growth was a significant gain. Since the beginning of the series in 1972, average annual real growth has been close to zero," said John L. Knapp and Robert W. Cox, authors of the study.

Cox attributed the continued rise to Virginia's healthy economy and the decrease in the inflation in 1984.

Any increases in salaries during the year were an improvement in the standard of living, not just an adjustment to inflation, Cox said. "It's a good trend, and the fact that we had two good years in a row is a sign that the economy may be growing again, not stagnating as it did during the 1970s and early 1980s," Cox said.

The median adjusted gross income (AGI) for married couples reached $27,987 in 1984. That marked a 6.4 increase, not adjusted for inflation, over 1983. (AGI is gross income minus a few deductions such as Social Security benefits, employer contributions and certain business expenses.) . . .

Northern Virginia led the state's eight metropolitian areas with the highest median AGI for married couples at $41,843, and more than 10 percent of couples there reported AGIs exceeding $75,000.

"We aren't able to tell what will happen in the future, and some would like to say we are at the mature stage of the business cycle. The 1984 report shows the increase in real income, but we'll have to wait and see if the turn continues upward," Cox said.

Conducted by the Tayloe Murphy Institute of the Colgate Darden Graduate School of Business Administration, the study is the 13th of a series that follows local distribution and increase of income in Virginia.

Based on information from the Virginia Department of Taxation, it covers all individuals and married couples required to file a tax return.

In 1984, half of the returns were filed by married couples, whose AGIs accounted for almost three-fourths of the total amount in the report. After Northern Virginia, the Richmond-Petersburg area was ranked second for married couples' AGI, with a median of $31,186. The Johnson City-Kingsport-Bristol area reported the lowest income at $19,196.

The incomes for married couples in other metropolitan areas of the state included: Norfolk-Virginia Beach-Newport News, $27,530; Charlottesville, $27,240; Roanoke, $26,635; Lynchburg, $25,599; and Danville, $21,925. Among the localities in the state, the five highest median adjusted gross incomes for married couples were all in Northern Virginia: Fairfax County with a median of $45,878; Fairfax City, $41,750; Arlington County, $39,774; Loudoun County, $38,017; and Prince William County, $37,841.

The counties with the lowest incomes were Lee with a median of $16,573; Charlotte at $16,771; Northampton at $17,121; Grayson at $17,165; and Lunenburg at $17,305.

The greatest concentration of high incomes was in Fairfax County, where 43.3 percent of married couples' AGIs exceeded $49,999. But because of the high cost of living in Northern Virginia, their real income was about $6,000 less, according to Cox.

On a statewide level, the highest proportion of married couples, 18 percent, filed returns for incomes between $30,000 and $39,999; 4.7 percent had incomes of less that $5,000; and 4.6 percent had incomes of $75,000 or more.

The median AGI for individuals -- single, divorced or widowed taxpayers -- rose to $9,765, an increase of 5 percent over 1983. In this category, Northern Virginia had the highest median AGI of $13,623, and the Johnson City-Kingsport-Bristol area had the lowest at $8,173.

Planning Research Corp. of McLean received a contract from the Air Force Space Command to continue overseeing a high-tech system that enables the North American Defense Command (NORAD) to track and monitor objects in space.

The contract, for the operation of the Ground-Based Electro-Optical Deep-Space Surveillance (GEODSS) system, has a potential value of $34 million over five years, according to Planning Research.

The contract was given to PRC Kentron, a division of the Systems Services operating group. PRC Kentron has been operating and maintaining the GEODSS system since 1983.

The U.S. Air Force said a $6 million award was given to PRC for one-year operation of the GEODSS system.

GEODSS is one of several systems used by NORAD to provide tracking and imaging surveillance data for deep-space satellites. The system uses a computerized optical tracker that can identify man-made objects 3,000 nautical miles from Earth.

The system, based in Colorado Springs, Colo., has three operational sites at Socorro, N.M.; Taegu, Korea; and Maui, Hawaii. A new location in Diego Garcia will be added and a fifth site is projected in Portugal.

The System Service division of Dynalectron Corp. of McLean received a contract from the State Department last week to design and install security systems in a number of the agency's overseas facilities, according to a company spokesman.

Sixty percent of the work under contract is a continuation from a 1981 contract; 40 percent is new services.

The contract becomes effective June 1 and includes a base year, followed by four one-year options. It is valued at $25 million over the five-year period, according to Dynalectron.

The System Service division is a part of Dynalectron's Government Services Group and divides most of its work between the State and Defense departments. The Government Services Group has approximately 6,250 employes at more than 100 locations; group revenue totaled $220 million in 1985.