APOLLO Observing Aids

The APOLLO graphical user interface is a highly capable platform written in Python (by C. D. Hoyle) to interface with the Telescope User Interface (TUI: written by Russell Owen) and the APOLLO hardware control computer, called houston. The APOLLO GUI uses a Tk interface and employs Hippodraw to plot the real-time data gathered by the system.

On houston runs a multi-threaded C program called housctl (written by Eric Michelsen) that interfaces to the APOLLO hardware and provides a command interface for human control via command line or GUI connections.

Below is a screenshot of the the main tab of the APOLLO GUI. On this tab we can see:

• a summary of statistics for a data run (upper left);
• a telescope offset and pointing correction panel (top center);
• a command line entry box and command response window (center);
• informational and settable parameters for controling the system state (bottom);
• a status line at the very bottom for informational updates from houston.

Other tabs relate to:

• a lunar pointer, modeled after the graphical lunar pointer shown here;
• control of the data plot window parameters (axes, etc.);
• a summary of alarms: the tab turns red under a new alarm;
• control of an automated raster of telescope pointing;
• control of the APOLLO CCD (SBIG STV model);
• control over the APOLLO APD: allowing one to temporarily disable individual channels in the 16-element array;
• power state of the roughly 20 independently activated APOLLO devices;
• laser state control, power measurement, tuning.

An example of the graphical window is shown below. This is a moderate-strength run on the Apollo 11 reflector.

The plots, starting at upper left, depict:

• the pattern reflected by the last 40 fiducial (local corner cube) return photons on the 4×4 APD array
• the pattern of the last 40 lunar return photons on the array (see concentration of returned light near the top, suggesting a telescope nudge)
• stripchart of lunar return rate, seen here peaking at about 0.12 photons per pulse
• laser pulse energy (shot-by-shot) monitor
• the fiducial return (red) from the local corner cube, together with the distribution of fast-photodiode returns (blue: should be 800 bins wide around 2000)
• the rate of fiducial returns: red = all returns, including background; green = "registered" fiducials—those in the spike
• raw fiducial (red) and lunar (blue) returns in TDC units (1 unit = 25 ps)
• lunar return histogram: the reflector return is seen above the background (from bright moon, mostly)
• lunar photon rate: blue = all returns; green = "registered" lunars (within dashed-bar window)—most get zero, and a few get 1 photon, and there are a few shots with more than one return photon
• stripchart showing all photon events; real lunar events fit within dashed region, and tend to cluster

Another Example Screen

This was not a particularly impressive run (poor atmospheric conditions), but it does show a signal return from the Apollo 15 reflector.

The plots, starting at upper left, depict:

• the pattern reflected by the last 40 fiducial (local corner cube) return photons on the 4×4 APD array
• the pattern of the last 40 lunar return photons on the array
• the pattern of telescope offsets pursued in the run
• the pattern of transmit/receive beam offset during the run; the color indicates lunar return rate—the best spot is in the middle
• the relative phase between T/R optic and diffuser optic
• the fiducial return (red) from the local corner cube, together with the distribution of fast-photodiode returns (blue: should be 800 bins wide around 2000)
• the rate of fiducial returns: red = all returns, including background; green = "registered" fiducials—those in the spike
• raw fiducial (red) and lunar (blue) returns in TDC units (1 unit = 25 ps)
• lunar return histogram: the reflector return is seen above the background (from bright moon, mostly)
• lunar photon rate: blue = all returns; green = "registered" lunars (within dashed-bar window)—most get zero, and a few get 1 photon (in this crummy run)
• stripchart of lunar return rate, seen here peaking at about 0.12 photons per pulse
• (top of) stripchart showing all photon events; real lunar events fit within dashed region, and tend to cluster
• (top of) laser pulse energy (shot-by-shot) monitor
• (top of) laser power measurement monitor (performed occasionally)

There are a few more plot windows that are not shown here, but this gets at the core. Others relate to a "stare" mode, wherein we point the telescope at a star or at the moon, and record the flux (as a function of time and of position on the detector array).