2004-06 Dec. APE Engineer Data
Introduction
In June 2006, we installed the DEC APE electronic. This directory
contains data collect from the new ape while running the forth
TCS system so we can determine how well the ape is working and
get some calibration values for the new APE to do the
position->Declination calculation.
This page contains the data collected, and our results.
1. TCS1 and MCC APE.
TCS1 zenith position is: 00:00:00 19:48:06.0.
Look at tcs1 and MCC apes.
tcs1 MCC apes
---------- ----------
40:00:00.00 39:38:01
+19:49:34.0 19:48:06 (zenith)
+10:00:00.0 09:37:15
+00:00:00.00 -00:23:04
-20:00:00.00 -20:23:54
-30:00:00.00 -30:24:23
-40:00:00.00 -40:25:00
2. Switch to new APE.
1.1 For the dec axis, the daycrew must slew over for access to the mirror cell
Make sure that the tcs1 system is kept running.
1.2 Switch over to tcs3 Dec apes electronics.
1.3 record tcs3 APE position:
coarse_data:
fine_data:
1.4 Make sure position is loaded in forth TCS before removing brakes.
Here is the position initialization command:
hhmmss.ss ddmmss.s !START
3. Collect coarse Data.
Note: tcs position provided by the forth system using incremental encoders.
We move to various Declinations and recorded the coarse & fine data.
tcs1 coarse: fine: position
40:00:00 deg: 8060 31800 1473592
19:49:34 deg: 11796 26291 2123443
10:00:00 deg: 13603 32159 2456991
00:00:00 deg: 15435 32335 2784847
-20:00:00 deg: 19060 32781 3440653
-30:00:00 deg: 20854 33045 3768597
-40:00:00 deg: 22635 33380 4096612
4. Collect Fine Data
Take 4 deg. of data for 960 seconds at 15 as/s.
(started at 19:47:34.10 to > 23:47:34 at 15as/s).
Data is collected using the readdata command in the apes/tester.c program.
Here is the command to start it, for 10Hz and degrees format.
> readdata 0.1 1
Data files is: 050615-rawread_10hz.dat
(deleted 1st 10sec of data as we started collecting before tracking).
Then switch back to the old APEs.
Format of the data is:
timestamp esec r_raw t_raw r(dec) t(dec) pos(d) pos(rad) pos(deg or Tm) pos_rad_chg.
11:06:09.12 0.000 0x0000 0x0001 0 1 1 0.000001 00:00:0.01 Tm 0.000
timestamp - timestamp of sample.
esec - elapse second (of sample)
r_raw - resolver data (raw)
t_raw - transductor data (raw)
r(dec) - resolver data (decimal)
t(dec) - transductor data (decimal)
pos(d) - correlated position
pos(rad) - position as radians
pos(deg or Tm) - position as Deg or Tm string
pos_rad_chg - changed of position from last sample (radians).
5. Fine Data analysis
In step 4 we collect find data at 10 Hz with move at 15 as/s. This should
give us a constant velocity over a distance of 4 degees.
Graph of Coarse Data, Fine Data, and rad_chg over time:
Notice the RadianChange is not constant:
Most values are 0.000007989 (1.65 AS) but their are +- 0.03489567 (7201AS)
jumps.
Here is the graph of absolute position (coarse sensor decreasing, fine sensor increasing).
Graphs produced using this gnuplot script: 5.gp
6. Coarse Data analysis
I combined data collect in section 1 & 3 in this table: 6.dat
Don't understand the difference in Tcs1 position vs APE position.
I was able to fit data MCC_APE_rad to the Coarse position.
Function is dec_rad = 1.31744675536335087429 + -5.3238007831129-07 * ape_cnt
6_idl - directory contains the program, input data, and output.
Note output.txt file shows the fix is not very good, errors in about 400 arcsecond,
with -2400 arcseconds at 00:00:00 Dec.
7. Comments
The coarse & fine data have different polarity (coarse decreasing, fine increasing).
This need to be fixed.
The tcs1 system wasn't working properly, if you compare the tcs1 vs. mcc_apes position.
Normally the differences should be < 2 seconds, didn't notice this until later.
This would have ruined the data, but since the APE isn't working, it junk data anyway.