EBZ 26 Dec 96 - with input from CED and JFC Summer 96 EBZ Mar 17 1998 EBZ June 1998 SEG Dec 28 1999 MDI ALIGNMENT ------------- EXPLANATION - This document discusses pointing adjustments. For large changes, center the image by moving the legs with the ALIGNIT procedure. Then null the ISS loop to get xerror and yerror to be 2.34V. Then close the loop and the mirror will not move. For smaller changes and to fine-tune the coarse adjustment, adjust the image center by moving the mirror. To move the mirror, change the xoffset and yoffset with the loop closed. PROCEDURE - Script: * The overall plan is to: * Set up the TM screens and observing campaign * Make sure ISS loop is open * Adjust the legs to image center - as close as possible to x = 511.5 and y = 511.0 * Null the ISS offsets and re-close the loop * Fine-tuning adjustment . * Do an open d on the egse . * Make sure a full disk continuum campaign (fd_f1_c1 (1070) or p30c_fd_m1 (2116)) is running. The IDL program monitor_center is reporting up-to-date values for the location of disk center on the current image. Example: IDL>monitor_center 980305_0100 DPC = 404b1fc0 COMPRESSED data 19 1 5-MAR-98 01:58:47 511.53 510.70 492.95 1775.6 1089.5 c68a91da 404b1fc0 (the above listed information is: date, time, x center, y center, avg intensity, deviation of intensity, seqence id, data product code) * You will also want these TM pages up: . Screen 12 (general monitor) Screen 5 (Mechanisms) Screen 8 (Limb Tracker) Take a screen 5 snap before and after starting leg movement Take a screen 8 snap before and after nulling and adjusting ISS . * perf alignit_v16 NOTE: alignit_v16 wants the center to be at 511.5, 511.5 and we want the center to be at 511.5, 511.0 so always add .5 to the y center before moving the legs . *** ADJUST THE LEGS *** . You do have the data - get it from monitor_center . In alignit_v16, click the "ADJ.LEGS" button. . It will open the loop *this must be done before anything else*. It will ask you for the present pointing - center of image in x and y (get this from monitor_center). Wait until the iss loop is open and the position moves to the null position and then use those numbers. It will ask if you want to turn leg power on - select yes. It will calculate the stepping needed to align motor 1 and 2 and it will return the calculated data in the form of: Projected motion (AM1,AM2): 6,-3 which means align motor 1 by 6 steps and motor 2 by 3 negative steps. Screen 5 has the AM1 and AM2 positions so see this change as the legs move. It will then move the legs and you should check monitor_center to see how close you are to the desired center of 511.5,511.0. When you are satisfied with the coarse pointing, get back to the alignit main menu and select null/lock iss. To speed things up, exit alignit, do an open d, and restart monitor_center to check the pointing. . If you want to try again, you must exit the program and re-run it, so hit yes and continue when it asks if you are getting closer and then let it finish file. Then re-run alignit_v16 to try it again. . When you are satisfied with the disk center location, go back to the main ALIGNIT menu. . *** NULL OFFSETS; CLOSE ISS LOOP *** Select NULL/LOCK ISS button in alignit_v16 . DO NOT select pictures - it will blow up if you select this option Keep answering the questions - yes, iterate, continue, in order to null the ISS x and y offsets. When this procedure detemines that x and y average error is about 2.3 (+/- .2) by adjusting the x and y offsets to make it so, you will be asked if you want to close the loop. Hit yes, and then use existing gain. Make sure the position doesn't jump when the loop is closed. When it has closed the loop, you can do fine-tune adjusting using alignit (see below) or you can do the microadjustments separately and so quit alignit and turn leg power off. . Remember to check that the AM leg power switches OFF on the power and/or mechanisms TM screens. . *** FINE-TUNE IMAGE POSITION *** . This can be done by manual tcblock commands: The x and y positions are adjusted as follows: X correction = 0.4*yoffset(n) => (tcblock mbltyofs Ny+n) Y correction = -0.4*xoffset(m) => (tcblock mbltxofs Nx-m) Where Nx and Ny are the current values of the x and y offset values. The offset values are listed on screen 8. The unknown values in the above equation are the x and y correction - solve for them. Note that the ISS x and y axes are rotated from the CCD image axes. For example, if the image center is at (512.2, 511.8), the x axis adjustment would be -0.7 and the y axis adjustment would be -0.3 in order to put the image center at (511.5, 511.5). Thus the yoffset would need to be set at -2 and the xoffset set at +1 in order to make this adjustment. It should be remembered that the -2 value needs to be sent as a 2's complement number. Thus the actual commands would be: tcblock mbltyofs 254 (X correction of -0.8 pixels) tcblock mbltxofs 2 (Y correction of -0.4 pixels) The limb tracker page lists the x and y offsets - these are the numbers you want to change when sending tcblock commands. To decrease the pixels you want to increase the offset. Examples: current x offset is 209 and monitor_center says that y=510.7 so it is too low by 0.3 pixels. So to add .3 pixels, send the following command: tcblock mbltxofs 208 current x offset is 214 and monitor_center says that y=512.6 so it is too high by 1.6 pixels. So to decrease by 1.6 pixels, send the following command: tcblock mbltxofs 217 EXAMPLE: Monitor_Center is telling you that the current center is 510.38, 512.17, thus if you subtract those values from the nominal values 511.5, 511.0 you will see they are off by 1.12, 1.17 respectively. Next, you see the current x offset from the limb tracker page is 212 and the y offset is 241. Using the equations above X correction = 0.4*yoffset(n) and Y correction = -0.4*xoffset(m), plug in the numbers that you know as follows: 1.12 = 0.4*n (solve for n) n = 2.8 1.17 = -0.4*m (solve for m) m = -2.925 NOTE: You must use a whole number, you cannot use a decimal number, thus you must use your judgement to determine whether or not you want to round up or down. You may want to round down and then see if you need to fine tune the legs a little more in that direction instead of overshooting the first time. Therefore, for this example, we will choose n = 3 and m = -3, since the actual numbers are so close to 3. Now that you have solved for n and m, plug those values into the equations above, Ny + n, Nx - m, where Ny is the Y offset from the limb tracker page and Nx is the X offset. See the following: Ny + n = New Y Offset 241 + 3 = 244 Nx - m = New X Offset 212 - (-3) = 215 Now, 243 and 215 are the new offsets that you enter using the tcblock commands: mbltxofs = 215 mbltyofs = 244 . Notes: Desired LEG center is as close to (511.5,511.0) as practical with the offsets in a neutral position. . The final image center after both leg and mirror adjustments should be (511.5,511.0). . The motor tcblock commands are: mbam1inc, mbam1dec, mbam2inc, mbam2dec Each takes a number of steps (as in "tcblock mbam1inc 2" to increment mbam1 by two steps). . The motors are offset by something like 60 degrees, and aren't quite orthogonal. The AM1 positive direction (+AM1) moves the IMAGE SSW. The AM2 positive direction (+AM2) moved the IMAGE NW. . A single step of either motor moves the image about 0.75 FD pixels. . To null the ISS separately from alignit: Run setup_iss_v08 to null the ISS error signals and close the loop. Use the current values of the gains: (99,87) for x and y, respectively. When done, exit setup_iss_v08; make sure that the loop is properly CLOSED, all PZTs are in range, the error values are low, and the disk is still properly positioned (according to MONITOR_CENTER). * Do an open d on the egse