1. STO Test Flight Strawman
3 Sept 2008
Preliminary schedule
Engineering tasks
Sensitivity estimates and mapping sequences
Estimated science deliverables
JHU/APL Flare Genesis ready for launch in Jan 2000
(STO gondola & telescope!)

2. Strawman flight schedule
Launch at sunrise; descend after astronomical twilight. ~14 hours total
This schedule is very “success oriented”; engineering exercises are likely to absorb most of the morning
Galactic plane is visible early and late in the flight
North Galactic pole transits around midday, so no choice but to schedule high latitude clouds
We need to continue after sunset to maximize Galactic Plane observability if flight trajectory allows.

3. Target Visibilities
NM time
is UTC-6
descent
elevation
in deg.
launch

4. STO Shakedown Aliveness tests, command and control
Pointing control and stability, star tracker tests
Initial instrumental calibration on Moon/Venus
Observation of a bright line source as sanity check
Move onto science targets, with continuing engineering exercises throughout

5. Pointing Sources Moon is only occasionally available, as shown at left
below
horizon
Moon is only occasionally available, as shown at left
Venus is at ~28 deg elongation, 12” angular extent
CO line pointing on CW Leo using 330 GHz Schottky receiver
good
high elevation
limit
good
sun avoidance
below
horizon

6. Possible Mapping Sequence for STO
STO's observing strategy is driven by the limited Allan variance time of HEB mixers!
Estimate 30 second OTF scans as per Allan variance measurements from J. Kooi w/ HIFI
Long slew+settle time of gondola means that we probably cannot use standard position switched OTF. Beam-switch OTF is also messy. An alternate plan is to use internal cold loads for immediate reference.

7. Mapping Strategy (cont'd)
need to repeat strip map 8 times to reach desired S/N at 15”/s
efficiency does not include spectrometer duty cycle = 95% at 1sec
ignore this column for a 1D map!
3s = 1K
For this scenario, we'd achieve a 1-dimensional strip map w/ 1.1 degree length to the targeted GPS sensitivity in ~1 hour. Assumes that we convolve 2-channel frequency resolution to 4 MHz = 0.6 km/s.
Note: 1 K km/s is equivalent to 7 x 10-6 erg/s/cm2/sr at the [C II] frequency

8. P/k ~ 1.4x105 exp(-R/5.5 kpc) K cm-3
Sensitivity comments
Detecting diffuse clouds in the process of becoming GMCs represent the most challenging observations that we will propose.
How bright will the lines be in the Galaxy?
Model Galactic clouds in [CII] using escape probability code; level populations computed assuming collisions with e-, H and H2
Ambient ISM pressure using scaling relation from Wolfire et al and assuming Pthermal = 0.1 Ptotal
P/k ~ 1.4x105 exp(-R/5.5 kpc) K cm-3
Typical line strengths:
3 K km s-1 per 1021 cm-2 hydrogen column at R=3 kpc
0.5 K km s-1 per 1021 cm-2 hydrogen column at R=8.5 kpc
0.1 K km s-1 per 1021 cm-2 hydrogen column at R=11 kpc

9. Science Targets
Strip map across bright sources w/ existing data: OMC, M17 (SW) etc...
Use IR extinction + HI and CO maps to identify region for an initial “L-strip” to perform during the test flight. The same techniques could be used to identify the precise regions to map for the Antarctic flight's Deep Surveys.
Example: the Polaris Flare at 100um

10. Science Return realistic case:
engineering tests run until 3:30 PM MDT; we go into science mode for last 3-5 hours of mission
2-3 hours on M17 = 2 strip maps of ¾ degree length (i.e. a cross map) at GPS sensitivity
2-3 hours on Galactic Plane = 1D strips on Galactic Plane (see below for 2 schemes)
cross-cut
2 deg. each
4 degrees
Spitzer NIR (GLIMPSE) map from l = 30o to 50o

11. Science Return (cont'd)
Optimistic:
engineering tests complete ~10:30 AM MDT; we go into science mode for last 6-10 hours of mission
Add to “realistic” plan the following
2 hours on Polaris Flare
1 hour on NGC 2264, Rosette, or Orion if we are extremely early