For the Space Shuttle, the local acceleration due to gravity was calculated onboard based on the vehicle position. So, as you say, they kinda did "carry a 'Gravitational Ephemeris'” > Because the vehicle's location changes with respect to the Earth as it > orbits, the state vector is constantly changing, and nav is > continually having to recompute it. This is done in the General > Purpose Computers (GPCs) via an algorithm known as “super-g > navigation.” The Super-g Algorithm performs the following functions: > > a. Given the state vector and gravitational acceleration from the last > cycle, a new position vector is estimated using either modeled drag > acceleration or IMU-sensed acceleration. > > b. The gravity at the new position is calculated. > >c. Using the change in gravity from the past > to the current cycle, the position and velocity vectors are > recomputed. From [Guidance and Control / Insertion, Orbit, Deorbit Training Manual][1] paragraph 2.3 More information about the gravity model is available in the [FDO On-orbit Console Handbook][2] paragraph 3.5.1.1 > The Orbiter's gravity potential model utilizes an infinite series > expansion of Legendre polynomials called Pines method. This recursive > algorithm accesses a database of harmonic coefficients arranged in > lower-triangular-matrix form. An element of the database is termed > Jn,m, where the row n is the harmonic's degree and the column m is its > order. When m=0, the coefficient's effect is symmetric about a > parallel of latitude, and it's termed a zonal harmonic. When n = m for > a matrix diagonal coefficient, its influence is symmetric about a > great circle of longitude, and it’s termed a sectorial harmonic. No > latitude or longitude symmetry is associated with the action of > coefficients having n ≠ m, and they are termed tesseral harmonics. The > onboard model is configured with a Goddard Earth Model 9 (GEM9) > database truncated to fourth degree and order. [1]: https://www.ibiblio.org/apollo/Shuttle/Crew%20Training/G_C%20Insertion%20Orbit%20Deorbit%20Workbook.pdf [2]: https://www.ibiblio.org/apollo/Shuttle/MCC/FDO%20Console%20Handbook%20-%20On-orbit.pdf