Cosmic Origins Spectrograph Instrument Handbook for Cycle 17

9.3 Spectral Element Movement Overheads

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For any COS exposure, including target acquisition exposures, an overhead must be included to allow for the time required for any change of spectral elements. Note that a transition from FUV to NUV may require both OSM1 and OSM2 to be moved as this transition requires movement of OSM1 to the NCM1 position, followed by a possible OSM2 movement. On the other hand, a transition from NUV to FUV requires only the movement of OSM1 from NCM1 to the desired FUV grating. Table 9.3 gives the times required for movement between all OSM1 spectral elements and Table 9.5 gives the times for movement between OSM2 spectral elements.

As there are setup overheads associated with moving and seating the COS OSM assemblies, you must add 60 seconds to the values in Table 9.3 and Table 9.5 to obtain the complete overhead required for the movement.

Note that all COS visits start with OSM1 at the G130M position and OSM2 at the G185M position.

Table 9.3:

Table 9.4:
 

Movement times (sec)1	to G140L	to G130M	to G160M	to NCM1
from G140L	-	96	138	53
from G130M	102	-	50	54
from G160M	144	54	-	97
from NCM1	59	47	92	-

1Add 60 sec to each indicated time to get the total time needed.

Overhead Times for Motions Between OSM1 Spectral Elements
Table 9.5: Overhead Times for Motions Between OSM2 Spectral Elements

Table 9.6:
 

Movement times (sec)1	to G230L	to G185M	to G225M	to G285M	to MIRRORA	to MIRRORB
from G230L	-	147	78	114	43	37
from G185M	142	-	74	40	107	113
from G225M	73	79	-	46	38	44
from G285M	108	45	41	-	74	80
from MIRRORA	38	112	43	79	-	9
from MIRRORB	32	119	50	85	15	-

1Add 60 sec to each indicated time to get the total time needed.