Goddard Infrared Camera

Also known as GIRCAM

For those of you who don’t know who GIR is. He here is. He’ll be helping us with the discussion.

Below, we’ll discuss how to start up the instrument and get it ready for observations.

Just in case, the powers that be do not setup the telescope right for the GIRCAM. Be sure and check the blue rack in the observing room.

Make sure that the knobs and switches look like the following.

The two most important points are labeled A and B. A is for the input selector (the knob). Be sure that the knob is turned to “Hold Mirror at Center Collimated Position”. B is for the toggle switch. Be sure that it is set to the center position labeled “CHOP”.

Go get the instrument box (and the instrument should be in the box) and proceed to the lab (i.e. where the pump and bolts are).

Get out the instrument and set it on the table next to the pump just like Chip did.

OR you can place it on its shipping box for pumping (which is what we did in a sec).

Be sure to have some GREASE on hand (it’s for the pump, not you). It should be an orange tube somewhere on the east side of the lab (at least, that’s where we got it).

When stored, the instrument should still have the vaccum chamber “sealed”. That is, the knob should be tight on the seal. You’ll want to open it slowly (like the dead or a quarter-turn per second for a more measurable estimate). Then, once the air escapes, you can then open the valve full throttle. Chip, our lovely assistant, is demonstrating for you the proper procedure for turning the knob (highly scientific stuff here).

The next step is to READ THE INSTRUCTIONS FOR THE PUMP.

I’ll say that again. READ THE INSTRUCTIONS FOR THE PUMP.

The instructions are located above the pump. If you didn’t see them, then maybe GIR got to you.

Scary…….

A few of the finer points to point out about the pump.

First, make sure that all those screw-fastening rings are tight around the plastic tubes. Wouldn’t want a tube to fly off and smack you in the head.

Here’s a picture of the rings that I’m talking about.

Smear some grease on the end of the GIRCAM’s valve.

Next, stick the end of the pump’s hose onto the valve. BE SURE THE PUMP IS NOT ON IN ANY WAY. That is, BE SURE YOU READ THE DAMN PUMP INSTRUCTIONS!

Tighten the screw fastener ring on the valve’s extremity. Again, make sure it’s really snug.

Once all the ends are attached and the rings are tightened, you can start the pump. The on switch is on the right hand side of the device (lower shelf of the pump cart). Turn it down to give the pump power.

Next, press the start/stop button on the face of the pump device. This push button is blue and says (amazingly) Start/Stop. Once you press this, you should hear the pump start.

The pump will go for awhile and try to reach a modest vacuum. Then, four lights will light up above the start/stop button. As of August 2004, only 3 lights lit up.

Here they are. Once this happens, the molecular turbo pump starts.

The molecular pump has to go for awhile on the instrument until the pressure reaches a Torr value of ???.

You can check the Torr value of the pump using the circle button located on the lower panel of the pump machine and shown on the image below.

Now, when the value of ??? Torr is reached, we can put liquid nitrogen into both wells.

Then, the pump runs for a few more hours until the Torr value reaches 3E-6 or so.

Once this value is reached, pour out the liquid nitrogen from both wells back into the cistern. Roll the instrument around to make sure that the last bits are out of the wells. ESPECIALLY THE WELL FOR THE LIQUID HELIUM. Any liquid nitrogen left in the helium dewar is a big pain in your ass if it’s still in there.

Once this is done, the pump part is over. Tighten the valve again. Turn off the pump (just the start/stop button). Then, the instrument is ready for liquid helium filling and liquid nitrogen dewar filling.

Liquid Helium Fill

You want to fill helium first because if you fill the nitrogen and it gets into the helium dewar, you’re gonna have some explaining to do (a very bad thing).

The helium dewar is the central hole located in this picture.

First, have a pair of gloves when dealing with liquid helium.

Next, get out the transfer rod.

Make sure the end going into the helium dewar is clean and NEVER touches the floor or anything else but air.

Next, turn the first emergency release valve to its off position (perpendicular to the pole). The emergency valve in this picture below points to the upper left. It has a yellow handle. In the image, the release valve is turned off.

The long transfer end goes into the tank. It’s placed into the red valve. In the picture above, the red valve is closed. It should be turned up to let the rod go in.

Turn the valve up and stick the rod in. Place it all the way in. The rod has a brass lock bolt on it. Push the rod in and place the brass lock directly onto the tank’s valve and screw them together.

Note that the red handle is turned up to let the rod go in.

During the time that it is sticking into the tank, the pressure inside will increase. NEVER LET IT GO ABOVE 5 PSI. Here’s a picture of the gauge.

If it does go above 5, use the other emergency release valve to release some of it. This other emergency valve is located in the picture below.

Now, the other end should go into the helium dewar. Brian, below, is about to do that. Be sure and stick the end of the rod into the dewar after you see cold helium gas spewing out the end in a white plume. In Brian’s case, it’s about to go in.

Now, when you first stick the rod in, the helium will spew out at great volumes because it’s too darn hot. Eventually, the pressure will die down. The pressure increases at the end because it’s full.

After the dewar is full, remove both ends of the transfer rod and turn off the red valve (red handle) and turn on the first emergency release valve (yellow handle).

Place the rubber hosing over the helium dewar to insure that nothing gets in.

One thing that cannot be photographed but is important is that condensation may form on the top of the instrument. These sites of condensation must be removed by blowing them off as soon as possible or wiping it off (once you’re done with the helium fill).

Now, it’s time to fill the nitrogen dewar.

Liguid Nitrogen Dewar Fill

This is a lot easier. The nitrogen dewar hole is right next to the helium dewar fill place. In the helium dewar fill image above, the nitrogen dewar hole is covered by its rubber hosing.

Now, pour out the liquid nitrogen into the high-tech transfer bucket.

Take the dewar filling hose and place it into the nitrogen dewar hole. Then, pour the nitrogen in.

You’ll know it’s full when it starts spilling out the hole. BE SURE TO BLOW OFF ANY REMAINING CONDENSATION AND LIQUID NITROGEN.

Pour the excesses are placed back in the tank.

Now, you just have to sit and wait for the thing to cool down.

One hour before sunset (this fill is done in the late afternoon), you must refill both dewar in the same steps as those given above. After this second fill, it’s time to set up the instrument on the telescope.

Instrument Installation

Be sure no power is going to anything related with the instrument, its controlling computer, or the preamp. If you don’t, GIR will sing you the DOOM song.

First, install the cords onto the back of the controlling computer rack. The pin holes are all labeled as well as the cables. Follow the labels and common sense and you should be fine.

Above, this is what it should look like in the end.

Next, install the temperature control cable onto the instrument. The temperature cable is the black one. If you desire to measure only the temperature at this time then this is the only thing you have to do. The installed black cable should look like this.

Next, install the two white cords. First, install the lowest (see image above) first. If you don’t, it’s just going to be a bigger bitch to put on.

Finally, install the preamp cable to the instrument. This cable has platinum (or some other fancy metal wiring) cables within it. Make sure that no stress is placed on these cables at all times.

The end of the cable that goes on the instrument is four separate white cable ends with gold connectors. Each has a number which corresponds to the exact same number on the instrument. The installed finished step looks like this.

Now, all the wires are in place. It’s time to install the instrument onto the telescope.

Lift up the instrument to the end of the telescope using the lift. Then, be sure and remove the plug over the instrument’s optical path.

Get the appropriate hex nuts and hex nut drivers. You’ll have to lift the instrument a little to get the aluminum plate of the instrument flush with the end of the telescope (shown below).

Screw it into place and you are done.

Next, secure the preamp to the side of the instrument’s aluminum light path. Duct tape works the best.

Next attach the remaining cables from the computer rack to the preamp. These should be placed on the output labeled side of the preamp.

Next, attach the instrument-to-preamp cable to the preamp.

Now, turn on the computer.

Then, flip the switch on the front of the computer rack.

Startup the appropriate software and turn off the monitor. You’re ready to observe.