She began employment activity as an engineer-observer at the Astrophysical observation station of the Astronomical Observatory of Leningrad State University in Byurakan (Armenia).
She is one of creators of the numerical Ephemerides of Planets and the Moon (EPM) of IAA RAS that originated in the seventies of the past century and have been developed since that time.
[2] The works of Pitjeva have recently been used by several scientists to test several models of modified gravity in the Solar System.
Recently Pitjeva collaborated with E. Myles Standish and proposed to the IAU Working Group on Numerical Standards for Fundamental Astronomy (NSFA) the values of the masses of the three largest asteroids, the Moon-Earth mass ratio and the astronomical unit in meters, mainly obtained while fitting the constructed DE (JPL) and EPM (IAA RAS) planet ephemerides.
Pitjeva gained her PhD in the field of "Astrometry and Celestial Mechanics" in 1994, with the thesis “Improvement of ephemerides of the major planets and determination of some astronomical constants by radar observations", and earned the Doctor of Science degree, the highest (after PhD) scientific degree in Russia, with the thesis "Construction of high-precision ephemerides of the major planets and determination of some astronomical constants", in 2005.