The orbits of the two satellites 1963-24B (Tiros 7 rocket, at inclination 58.20) and 1974-34A (Intercosmos 11, at inclination 50.60 ) passed slowly through 15th-order resonance within 6 months of each other in 1976-77. The changes in their orbital inclinations and eccentricities have been analysed, using 112 weekly US Navy orbits for 1963-24B and 129 for 1974-34A. The analysis has yielded 16 values of lumped harmonie coefficients, 12 of 15th order and four of 30th order. Sixteen equations are given for these lumped harmonies in terms of the individual coefficients of order 15 and 30, for use in a fut ure determination of the individual coefficients. The lumped harmonic coefficients obtained from the two satellites have been compared with the corresponding values from the latest Goddard Earth Model (GEM IOC). The agreement is very satisfactory.