The COBE Far InfraRed Absolute Spectrophotometer ( FIRAS ) observations constitute an unbiased survey over the wavelength range from 100 \mu m to 1 cm over 99 % of the sky .
Improved calibration of the FIRAS instrument and the inclusion of all of the FIRAS data allow an improved signal to noise determination of the spectral lines by a factor of \sim 2 over our previous results .
The resolution is low ( 0.45 cm ^ { -1 } ) so only the strongest lines are observable .
The CO chain from J = 1 - 0 to J = 8 - 7 is observed towards the Galactic center .
The line ratios are roughly consistent with a 40 K excitation temperature .
The 157.7 \mu m C ii and 205.3 \mu m N ii lines are observable over most of the sky .
The 370.4 \mu m and 609.1 \mu m lines of C i , and the 121.9 \mu m line of N ii are observed in the Galactic plane .
The line ratios at the Galactic center are consistent with a density of n _ { 0 } \sim 30 cm ^ { -3 } and a UV flux of G _ { 0 } \approx 15 ~ { } \mu W m ^ { -2 } sr ^ { -1 } ( 10 Habing units ) .
The 269 \mu m H _ { 2 } O line is observed toward the Galactic center in absorption .