Progress report 28 September 2004
Progress since the last report has been slow in
some areas but it's fair to say that things are moving a pace at the moment. In
no particular order, here is where we are:
"This Space for Science"
With the ideas for this reduced to two at the last report a more detailed look was undertaken at the final contenders. They are a simple ozone experiment and an active Attitude Determination and Control for the spacecraft. Of the two it was obvious that the former was very much dependent on the latter and the major effort and resources - both manpower and financial - have been concentrated on the systems and equipment necessary to support the ADAC aspect. As a result, a considerable amount of work has been undertaken to improve and develop the basic systems covered previously and we have now extensively tested the final designs for the Earth/Horizon sensor and the Sun Sensor. Both have been produced using home brew PCB's using 'through hole' technology which - with its 'wide open spaces' - allowed us to make any modifications with reasonable ease. Happily none was required and both boards are 'as etched'.
Now well proven, the schematics are currently being converted into the necessary SMT artwork and it is intended that both systems will be incorporated on one board to reduce the component count. The variable resistors will be "installed" on a system of pads that will support their replacement by fixed resistors once the sensitivity levels have been set. In tandem with work on the electronics, it was decided to revisit the sun sensor head with a view to reducing its size and weight. The reworked heads - two will be flown - are complete and tested and a saving of over 50% on size and weight has been made. Well worth the effort when looking at launch costs of around US$10 /gm! A 3 axis Honeywell magnetometer head has been acquired and in keeping with the policy of "mock up and try" whenever possible, a graduated gimbal fitting has been produced to enable the unit to be 'worked' as far as practical in an earth bound environment. Only the 25mm x 18mm PCB - located in the centre of the picture - will fly. (!!) As previously mentioned it's hoped to include a GPS receiver. This will be coupled into the L band Rx antennas. Unfortunately, a suitable unit - at a price we can afford - is proving elusive. As some will know, the 'standard' GPS, now very cheaply available over the counter, is only accurate at speeds up to (approx) 2000mph and at altitudes below 60,000ft. With KiwiSAT travelling at 18,000mph and in orbit at an altitude of 500 miles, a 'standard' unit falls somewhat short of the mark! The bottom line is that we can't afford a 'high speed' version at the present but things may change and to keep our options open we are making allowance for GPS in the satellite. In the absence of the required version a 'standard' GPS board is down to fly. It's understood that the positional data from this will be of no value but we need an accurate clock on board and the 'terrestrial' version will give us a very acceptable timekeeper if nothing else. A suitable board is currently to hand and this has been fitted with a screening box with a view to integration of it - or a suitable replacement - into the final layout.As can be seen, considerable work has been done on the ADAC aspect. That does not mean that the ozone experiment has been abandoned - it's still there but on the 'back burner' for the time being.
Initially one of the slower systems, large strides have been made during the past few months.With little to show a year ago it was decided to convert commercial Tx and Rx boards and - with a suitable keyer - to make up a cross band repeater for use (initially) in the Auckland area. It was felt that this would put the project on the map and it would also serve a dual purpose. It would be installed and run from the vacuum chamber loaned by Massey University in its Albany Campus on which the temperature cycling facility needed to be set to work. For added realism the antennas to be used would be those on the test module set up by Terry (ZL2BAC). As it turned out other work prevented much activity on the thermal side but the RF trial proved successful. The two experimental units - supplied by Salcom Ltd. - and engineered into the repeater by Kelvin (ZL3KB) was on the air for several months as ZL6SAT. Not ideally situated in Albany as the district is very much in a low lying 'bowl' the unit was, however, worked by many local stations and was finally shut down in June when the lessons learned enabled work on a flight-qualified unit to be taken in hand by Kelvin. That is progressing well and the Tx flight design has been bread-boarded. It delivers either 1 or 2 Watts with good efficiency and it's worthy of note that lengthy research was necessary to identify materials and then rework the coil formers using space worthy plastic material. (Space materials again…!) The PCB artwork is with a board manufacturer and mid October should see the first flight/engineering board up and running.
Work on the U/V transponder is currently shelved whilst attention is diverted to the design and build of a transponder unit for Phase 3E (Express) in support of AMSAT-DL. There are clearly significant differences between the U/V transponder for P3E and that for KiwiSAT but there will certainly be some spin off between the two and AMSAT-ZL is delighted to be given the opportunity to contribute to the '3E project. We will certainly learn a lot from the experience and the inevitable delay to the RF aspect of KiwiSAT will be well worth it in the long run. The transponder effort will not have any major affect on the other systems of course. Work on them goes on.
Of all systems to take a leap forward over the past year, the IHU is the 'cherry on the cake'!
Lyle Johnson (KK7P) visited us earlier in the year and by the time he left we had the makings of our IHU. Many thanks, Lyle! We have now - with his continued help and that of Chuck Green (N0ADI) - got to the stage where we are have the artwork ready to produce the necessary 4 layer PCB's. Our thanks to professional PCB designers Hans, Simon, Nick, and Kevin from various New Zealand electronics companies for their sterling support.
We are investigating the supply of components for four sets of IHU boards. These will be used for development with one reserved for eventual flight. With the computer hardware finalized the detailed work on the software is also firming up and Daniel (ZL1DFA) - who is leading our software team - has many far-reaching plans that can now come into their own. A most productive and encouraging few months.
The decision has been made to use high efficiency (28%) solar cells and we are currently looking at ways of financing their acquisition. The use of a lesser efficient and very much cheaper cell was not seen as cost effective and despite the small numbers in AMSAT -ZL and the mammoth problem of raising the necessary funds, the challenge will be taken up.
From a battery point of view NZART Branch 12 (Hamilton) have volunteered to help with the battery choice and selection/matching task. We welcome Robin (ZL1IC) and his team on board and look forward to their input. It's always great to have fresh minds and support in any area and particularly so on the battery side. The failure of storage batteries has provided the final curtain for many if not all amateur satellites. They need to be right! Branch 12's offered involvement is a great boost.
In the meantime access to the Battery Analyser and other facilities provided by Massey University will be used to complete the 'familiarisation' work currently under way on both NiCd and NiMH cells. Hopefully a chemistry selection will be firm by the end of the year and a main and standby pack will be well in course of preparation. The basis of the Battery Charge Regulator has been well established by Hans (ZL1HB) and the detailed work will no doubt pick up when the battery pack parameters have been finalised.
The decision to use the high efficiency solar cells presents one immediate problem; they come in larger 'pieces'! Unfortunately a change is now needed to the existing solar panel outline and this has necessitated a small change to the overall size of the satellite. In addition to this modification the AMSAT-ZL proposal to plan for a Russian Dnepr launch means that the original release system - which was based on the 'sprung release' of the original MicroSats - will not now be suitable. Changes to meet the 'drop off' launch system that the reversing third stage of the Dnepr launch vehicle employs, must be made. Adding to the above, an offer by Mike Jack of Stanier Engineering to CNC machine the trays from solid aircraft alloy was too good to miss and this again adds a new perspective to the design. We are grateful to Mike for his offer and can confirm that all these design changes are being worked through. As a result, Fred's limited CAD experience is being extended and consolidated in the process; but no bad thing that! Work on the re-design will continue throughout the year.
Fred attended and much enjoyed the 2003 AMSAT-UK Colloquium and spoke on the KiwiSAT Project. This appeared to go down well with those attending and he subsequently made contact with several people who offered help and advice on several areas of the build. All extremely useful as we get into the real meat of the project. AMSAT-ZL was not represented at 'Surrey' this year but it's on the cards that perhaps two will be there for the 2005 event expected next July.
Material and processes to meet the very demanding conditions in a space environment remain a problem but access to the appropriate web sites has become easier during the past year. We can now at least identify - if not readily obtain in small quantities - the materials appropriate to the job! That problem is going to remain with us here in New Zealand and we would be delighted to hear from anyone, anywhere, that can help source "small quantity" space qualified materials.
Fund raising is still very much an issue of course, as is the need for more volunteers. Any input on either is very welcome and you will find a ready listener in any of the members of the AMSAT-ZL committee! The pace is increasing but it's never too late to join and work with the team.
Give it a go - you'll enjoy it!
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Last updated 02/10/2004