SWAS Prelaunch Page

table test

The SWAS satellite has been launch into orbit on December 5, 1998. The drop of the Pegasus rocket occured at 16:57 PST and SWAS was release from the 3 stage at 17:10. Since then, the SWAS satellite is operating and producing lots of data.

The SWAS launch could be seen from the California coast south of San Francisco to Los Angeles. If somebody took really nice pictures of the launch, we would appreciate to get copies (paper or binary are welcomed) so we can add them to our web page. Thank you.

The SWAS mission concluded in 2006 after analyzing the DEEP Impact data. However, the SWAS satellite is still orbiting Earth. It has been put into a sleep mode and could be reactivated if desired. More information about the SWAS mission can be found at the main SWAS webpage .

The test and integration schedule and the R-day schedule can be found on the SMEX-SWAS home page .

Email vtolls@cfa.harvard.edu

Prelaunch activities in chronological order:


  • Preparing for another launch attempt today.
  • 12:20 The weather looks fairly good for today's launch attempt. There is only a 20% chance of weather violation in the drop box due to cumulus clouds. Right now the weather is green. The extended forecast for tomorrow shows weather green with currently 0 % weather violation since the front that is pushing south today will be to the east of us.
  • Detail list of activities of the launch day .


  • Preparing for another launch attempt today.
  • 12:15 PST The weather briefing predicts up to 2 inches of rain for VAFB for this afternoon. Water on the runway would violate take-off constraints (possibility of skidding off the runway).
    Furthermore, they predict cumulus clouds in the flight path of the L1011 to the launch area. The rain in these clouds would violate weather constraints. However, there is a possibility that the L1011 can fly around the bad weather zone.
    The launch area itself is predicted to be free of bad weather, thus, clear for launch.
    Currently the weather is red (no launch), and the prediction is a 60 % probability of weather violation. The later the airplane will take off, the more likely we will have sufficiently good weather. Another update will come later.
  • Again, the launch was aborted!
    The L-1011 taxied down to the end of the runway and sat while mission management, NASA, OSC and analysts debated whether or not the mandatory Flight Rule # A23 could be changed from a ground speed of 900 ft/sec to 980 ft/sec. The proposed change would cause a slight change in the dynamic pressure causing a change of less than 1 sigma on stage 1. While OSC and most analyst agreed that the change was rather insignificant, from a management view and procedure view, a mandatory flight rule can not be changed once the check list has started.
  • Detail list of activities of today's launch attempt .


  • Preparing the rocket for payload testing
  • SWAS Launch Pad Functional


  • The final count down has started!
  • Activities:
    Remove SWAS Hot Pad GSE
    Install SWAS Arming Connection
    Closeout Fairing
    Power on and Configure SWAS for Launch
    Prepare OCA for take-off

  • 04:10 pm OCA ready for taxi, airplane is rolling
    04:43 pm OCA has taken off
    05:38 pm Launch aborted, initiating abort procedure
  • 05:48 pm Proceeding with Mission Recycle (trying another launch)
  • 05:53 pm Recycle Aborted
  • 05:58 pm Proceeding with RTB Procedure (return to base)
    A more detailed activity list can be found here .


  • Transport of the rocket from Building 1555 (OSC Building) to the hotpad. The hotpad is the place where the airplane is parked and thus where the rocket will be attached to the airplane. This operation happened at 5:00 in the morning in pouring rain.
  • Putting the airplane on jacks and mating of rocket to the airplane (see Pictures). Completed by 11:00 am
  • Check-out of all mechanical and electrical connections (Pegasus/OCA Compatibility Test) completed by 4:00 pm
  • Launch Pad Functional: Last major test of the SWAS spacecraft/instrument before launch.
    Started by 4:00 pm. Finished by 11:00 pm.


  • The Preparation for the SWAS Launch continue after the Thanksgiving Break
  • The roll-out of the SWAS rocket has been delayed until tomorrow because of bad weather (forcast of 1 in of rain and lightning). However, we are still processing for a December 2 launch.


  • Trend up/down
  • Group Picture of SWAS Team with Pegasus Rocket
  • Loading Pegasus onto transport trailer


  • Complete SWAS Battery Reconditioning and Trickle Charge
  • Port Fairing Installation

    High resolution picture (1280x960 pixels, 242k) of SWAS in the fairing (left picture above).
  • UHF/OCA Commanding Test


  • SWAS Battery Reconditioning


  • SWAS Battery Reconditioning


  • NASA Launch Readiness Review (LRR)
    Review of outstanding issues with the rocket or with the payload. Most of the issues could be closed out. Only a few have to be closed out over the next few days before the final OKAY can be given. Therefore, we will have a Delta LRR next week.
  • Installation of the starboard fairing
  • SWAS spacecraft battery reconditioning


  • Finish Installation of equipment in OCA (or OLC)
  • UHF/OCA Commanding Test at Bakersfield
  • Mission Dress Rehearsal
    During the mission dress rehearsal we simulated the launch of the Pegasus rocket with the SWAS payload. The first run was basically a simulation with everything running as expected, all data were within their limits. After the first run, an aborted launch was simulated, to make everybody familiar with this abnormal procedure.


  • Flight Simulation #4 Data Review
  • Ship SWAS ASE and PSS to Bakersfield
  • Install Equipment in Orbital Launch Carrier (OLC)
    Remark: Orbital Launch Carrier is another name for the airplane from which the Pegasus rocket will be launched.


  • Hot Pat Communication Test
  • Flight Simulation #4 (Launch Day Procedures)
    This simulation checks out and trains the people with the activities going on on launch day from preparing the airplane for take-off until separation of the payload from the rocket. All communication between the spacecraft and the ground operator go through the rocket telemetry.


  • Mission Operation Center Tests for as long as we have the range.


  • Finally a day off!


  • Spacecraft Blanket Work
  • Launch Pad Functional
    Today we are running the launch pad functional to verify the proper electrical mating of the spacecraft to the rocket.


  • Mating SWAS to the Pegasus rocket
    First we had to close-out a few issues concerning connectors. Then, the actual mating could happen.


  • Pre-mate Review
  • Installing payload separation ring
  • Mating SWAS to the Pegasus rocket
  • Spacecraft Blanket Work


  • Flight Simulation #3 (Launch Pad Procedures)
  • Spacecraft Blanket Work


  • Trend up/down
  • Flight Simulation #3 (Launch Pad Procedures)


  • Lift of spacecraft onto mating dolly
  • Interface Verification Test (IVT-Test)


  • Continued work on solar arrays
  • 3 solar array deployments
  • Trend up/down


  • Analysis of Noise Temperature Test data
  • Removing Noise Temperature Test GSE from SWAS
  • Turn over SWAS into vertical (upright) position
  • Work on Solar Arrays, Solar Array Deployment.


  • 5:37 am Delta II launch
  • Noise Temperature Test

    The test started with its preparations around 6:15 am. The instrument was powered up around 7:45 am. It took a long time to establish thermal equilibrium in the instrument since the LN2 boil-off rate was much higher than during previous tests. The higher boil-off rate caused more cold air within the GSE/Instrument enclosure leading to much lower instrument temperatures. However, we finally reached thermal equilibrium and could run several noise temperature measurements. Since we had a colder receiver, the measured noise temperatures were lower than for previous tests. The conclusion is that we had a successful noise temperature test with excellent conditions for the measurement itself.


  • Putting SWAS on the turn-over fixture
  • Power up spacecraft to check electrical connection which had to be removed for turn-over
  • Preparation for noise temperature test


  • Launch Pad Functional
  • ACS Phasing Test
  • Solar Array Cleaning
  • Solar Array Flash Test
  • Transient Battery Installation


  • Mission Readiness Review
  • Solar Array Deployment
  • Trend up/down


  • Arrival of the SWAS satellite at Vandenberg Airforce Base
  • Start of R-Day Schedule
  • Unloading trucks, setup of SWAS equipment, GSE and support material
  • Briefing of test personnel


  • Packing of SWAS equipment
  • Packing of SWAS satellite
  • Loading trucks and putting it on the road


  • SWAS Receiver PLL Test
    For this test we radiated with an RF source into the SWAS telescope. The RF source has had a very stable input reference frequency of about 5.1244 GHz. The 96 harmonics of this frequency is 491.94 GHz which produced a line feature in the lower frequency receiver. The lower frequency receiver can be tuned over +/- 25 steps, each step is a frequency shift of 12 MHz. For this test we stepped through all 50 steps and looked at our line feature. For a good lock of the receiver phase lock loop, the line feature should be narrow. For all steps in the lower frequency receiver it showed a linewidth of about 1 AOS channel giving a good lock.
    We repeated the test the the higher frequency receiver channel. Since the sensitivity of this channel is reduced due to water in the atmosphere and a 15 dB lower output power of our RF source, we could not detect a line feature in the AOS spectra with maximum input power to the RF source. It shows us again why we have to go into space to observe water.
  • Folding of solar arrays
  • Cleaning outside of spacecraft and instrument
  • Preparation for shipping


  • Successful commanded Solar Array Deployment
  • Launch Pad Functional
    Thorough engineering testing of the spacecraft and instrument by checking most of the functions through commanding and crossreferencing the housekeeping data.


  • Thermal Blanket Work finished
  • Storing the solar array for tomorrows deployment


  • Thermal Blanket Work


  • Thermal Blanket Work


  • SAO Timeline
    The test started with minor problems dealing with Y2K. Since the equipment was built for a 1995 launch, parts of the GSE have problems with Y2K. Figuring out work-arounds led to a late start of the test.


  • Launch & Early Orbit Simulations Day 2
    Continuation of the test started yesterday. At the end of the test, the instrument will come online.


  • Launch & Early Orbit Simulations
    These simulations are to train the Mission Operation Team for the upcoming SWAS launch. The simulation today will have known anomalies which the team has to resolve while online.


  • Preship Review



  • SAO Timeline Test


  • Turn-over Spacecraft.
  • Installing Multi-Layer-Insulation (MLI) Buttons.
  • Replace screws of Gore-Tex cover with flight screws.
  • Reconfigure Spacecraft for upcoming Simulations.


  • Near Field Range Test: Part II


  • Near Field Range Test: Part I


  • Preparing the Near Field Range Test


  • Noise Temperature Test

    In the noise temperature test, we measure the sensitivity of our radiometer at ambient temperature. The sensitivity is expressed as a temperature in Kelvin. The lower this temperature, the more sensitive is our instrument. After a long day we could reconfirm earlier test results. This means that our instrument is still in very good shape.


  • Preparing the Noise Temperature Test


  • Gas Cell Test: Water (Receiver Channel 2)


  • Gas Cell Test: Formaldehyde (Receiver Channel 1)

    In the gas cell test we place a gas cell in front of the telescope. Due to the large diameter of the telescope, the gas cell does not cover the whole beam. Thus, the outer parts are looking onto RF absorber, and only the inner part of the telescope beam goes through the gas cell. The gas cell is fill with 110 mTorr formaldehyde. Considering that ambient pressure is 760 Torr, we are using a very tiny amount, much less than a drop if it would be liquid. Now we are measuring the emission from the gas by looking onto a piece of RF absorber behind the gas cell which is at ambient temperature. Since everything is at the same temperature, we see only the broadband radiation from a blackbody at ambient temperature. In a second step we are looking at RF absorber at a temperature of 77.3 Kelvin (or -196 deg Celsius). Now we can see the a signal from the formaldehyde gas because the gas is much warmer than the RF absorber in the background. Further steps in the experiment involve taking several additional reference measurements. The final result looks like (TBD).


  • Preparation for instrument testing.
    Putting SWAS into place on the floor of the cleanroom, ready for setup. Cleaning of gas cell GSE and wrapping of instrument and GSE into an almost airtight tent for purge with gaseous nitrogen.
  • Continued preparation for blanket work.
  • Cleaning of other instrument test GSE for upcoming tests.


  • Blanket work
  • Power-on (no instrument turn-on)
  • Additional ACS testing Part II


  • Power-on (no instrument turn-on)
  • Additional ACS testing Part I
    This test has become necessary because problems could have developed in the ACS system, in particular with the reaction wheels and gyros, after the extended storage time. In order to make sure that everything is working as before, this test checks all important parameters.


  • SWAS spacecraft has been put onto its turn-over fixture, and tilted to the side as preparation for the upcoming ACS tests. All electrical connections had to be reattached since they were removed for safety and ESD reasons.
  • Delivery of the repaired gas cell.


  • Trend-up
  • Launch and Early Orbit Simulation Procedures
    These procedures simulate the launch of SWAS beginning with the drop of the Pegasus rocket from the L1011 Airplane, delivery of SWAS into its orbit, and the first couple of ground contacts with appropriate initial commanding for the spacecraft.


  • Trend-up
  • SAO Timeline Test
    The timeline started around 9:45 am and ended around 7:00 pm with the last simulated ground pass.
    The timeline day was 98 354.


  • Trend-up
  • SAO Timeline Test
    A few problems encountered when trying to set up the spacecraft for the execution of the timeline caused a delay of its start until about 3:00 pm. The timeline was stopped at about 7:00 pm.
    The timeline day was 98 349.


  • Trend-up
  • Test of Launch Day Procedures.
    The instrument will be turned off for almost the entire test. The procedures executed check out the spacecraft commanding and performance immideately after the launch.
  • Short Timeline Test
    Checking out the reworked timeline from the barker test. Now they were able to find 3 of 3 targets.


  • End of 28 hour Barker Timer Test
    Test ended around 9:34 pm with the timer expiring. Since it was not set to do so, the instrument stayed turned on. It was powered down immideately after the expiration. The timeline being executed during the barker test was commanded successfully. However, it didn't lock on any target since the wrong guide star positions have been used when the timeline was created. This cause a non-lock on all targets.


  • Trend-up
  • 28 hour Barker Timer Test
    The start of the barker timer test was delayed because of problems concerning the connection of the SWAS GSE with POCC and the failed slow uploading to the SWAS spacecraft from POCC (failed twice from POCC due to a reboot ACS dynamic simulator). The test started at around 5:30 pm. The timeline executed during the test didn't produce the expected result due to the wrong guide star positions. Otherwise, the barker timer timed-out around 9:34 pm on Saturday as expected.
    The timeline day was 99 004.


  • Trend-up
  • Command & Data Handling Functional
  • RF Long Functional
  • Reinstallation of swas_spectrum on GSE computers.
  • Unpacked gas cell test equipment. A broken valve on one of the gas cells will be fixed within the next days.



  • Trend-up
  • Successfully rerun of the Initial Acquisition Dynamic Simulation .
  • Safehold Dynamic Simulation (better Digital Sunpointing Simulation).
  • The update R-day schedule (Version 9/22/98) shows a December 2 launch.
  • Trend-down

  • note changes in the schedule for the upcoming tests


  • Trend-up
  • Initial Acquisition Dynamic Simulation failed because no data were stored after a power spike (?) caused a reboot of the ACS simulator computer.
  • Trend-down


  • Trend-up
  • ACS Software Long Functional
  • Trend-down


  • Trend-up
  • ACS Hardware Long Functional
  • Trend-down


  • Trend-up
  • Power Long Functional
  • Trend-down


  • Trend-up
  • Reconfiguring the air conditioning of the SWAS spacecraft and instrument to cool the instrument more efficiently.
  • Spacecraft Long Functional Test (with extensive instrument functional testing) finished successfully. All engineering data confirm the data measured during previous tests within their temperature caused variations. The mixer and tripler bias voltages are as before. Both laser diodes in the AOS are working with the same currents and power output on the monitor diodes. The comb spectra lines show no significant shift. All commanding performs as expected.
  • Trend-down


  • Anomaly close-out
  • Finalizing and testing the connection from the SAO computers to the ITOS system of the SWAS GSE. Everything is up and running now.
  • Trend-up/down


  • Anomaly close-out


  • Big day: first turn on of the instrument after about 1 year .
  • Trend-up/down
  • Instrument was turned on at about 10:30 am. The mixer and tripler readings showed about nominal values (slightly off by about 1 bit due to the temperature of the instrument). AOS laser diode 1 showed nominal current and power. The instrument temperature was about 22 C.


  • Connect the ACS system
  • Connect instrument GSE to S/C GSE
  • Close out anomalies occurred on 9/9/1998


  • Powered up S/C
  • Deployed solar arrays
  • Connected flight battery


  • Set up of the SWAS S/C GSE